Securing a second object to a first object

ABSTRACT

A method of mechanically securing a first object including a thermoplastic material in a solid state to a second object with a generally flat sheet portion, with a perforation of the sheet portion, and with the sheet portion having an edge along the perforation is provided, wherein the first object is positioned relative to the second object so that the edge is in contact with the thermoplastic material and wherein mechanical vibration energy is coupled into the assembly including the first and second objects until a flow portion of the thermoplastic material due to friction heat generated between the edge and the thermoplastic material becomes flowable and flows around the edge to at least partially embed the edge in the thermoplastic material. After the mechanical vibration stops, the thermoplastic material is caused to re-solidify, whereby the re-solidified thermoplastic material at least partially embedding the edge anchors the first object in the second object.

BACKGROUND OF THE INVENTION Field of the Invention

The invention is in the fields of mechanical engineering andconstruction, especially mechanical construction, for example automotiveengineering, aircraft construction, railway industry, shipbuilding,machine construction, toy construction, building industries, etc. Inparticular, it relates to a method of—mechanically—securing a secondobject to a first object.

Description of Related Art

In the automotive, aviation and other industries, there has been atendency to move away from steel-only constructions and to uselightweight material such as aluminum or magnesium metal sheets orpolymers, such as carbon fiber reinforced polymers or glass fiberreinforced polymers or polymers without reinforcement, for examplepolyesters, polycarbonates, etc. instead.

The new materials cause new challenges in bonding elements of thesematerials—especially in bonding a flattish object to an other object. Anexample for this is the bonding of parts of polymer-based material tometal parts, such as metal sheets.

To meet these challenges, the automotive, aviation and other industrieshave started heavily using adhesive bonds. Adhesive bonds can be lightand strong but suffer from the disadvantage that there is no possibilityto long-term control the reliability, since a degrading adhesive bond,for example due to an embrittling adhesive, is almost impossible todetect without entirely releasing the bond. Also, adhesive bonds maylead to a rise in manufacturing cost, both, because of material cost andbecause of delays caused in manufacturing processes due to slowhardening processes, especially if the surfaces to be connected to eachother have certain roughness and as a consequence the quickly hardeningthin-layer adhesives cannot be used. Further, a flattish adhesive bondbetween two objects not having the same coefficient of thermal expansionmay lead to additional reliability problems as the adhesive bond may besubject to substantial shearing forces in everyday use due totemperature fluctuations.

A particular challenge when bonding elements to each other is thecompensation of tolerances, for example if the elements are bonded toeach other with other bonds than adhesive bonds, such as by screws andnuts or by rivets. In such bonds, a precise definition or the relativelocations of a fastener and the respective fastening location isrequired. Such precise definition may especially be hard to reach if amanufacturing process has to be particularly economical and/or if theparts to be connected are comparably large in at least one dimensionand/or react to the conditions they are subject to during manufacturingand use in a different manner (for example if they have differentcoefficients of thermal expansion).

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodof mechanically securing a second object to a first object, the methodovercoming disadvantages of prior art methods. It is especially anobject of the invention to provide a cost-efficient method that yields areliable connection between a thermoplastic part and a part that is notliquefiable under the conditions, under which the thermoplastic partliquefies, or that yields a reliable connection between different partsby means of a thermoplastic connection element. It is another object ofthe invention to provide a method that yields a reliable connectionbetween parts and is efficient and quick. It is a further object of theinvention to provide a method that yields a reliable connection betweenparts and allows for an efficient tolerance compensation.

According to an aspect of the invention, a method of mechanicallysecuring a first object to a second object is provided, the methodincluding the steps of:

-   -   Providing the first object including a thermoplastic material in        a solid state;    -   Providing the second object with a generally flat sheet portion        with the sheet portion having an edge;    -   Positioning the first object relative to the second object so        that the edge is in contact with the thermoplastic material;    -   Coupling mechanical vibration energy into the assembly including        the first and second objects until a flow portion of the        thermoplastic material due to friction heat generated between        the edge and the thermoplastic material becomes flowable and        flows around the edge to at least partially embed the edge in        the thermoplastic material;    -   Stopping the mechanical vibration and causing the thermoplastic        material to re-solidify, whereby the re-solidified thermoplastic        material at least partially embedding the edge anchors the first        object in the second object.

In the step of coupling mechanical vibration energy into the assembly,the first object may be pressed against the edge so that uponliquefaction of the flow portion the edge is pressed into thethermoplastic material of the first object.

After stopping the mechanical vibration, a pressing force in embodimentsis maintained until the flow portion has re-solidified at least to someextent to prevent a spring-back effect.

In embodiments, the second object is provided to have a perforation ofthe sheet portion, with the edge running along the perforation.

In embodiments having a perforation, the sheet portion around theperforation has a projecting section projecting away from a sheet planetowards the first object, i.e. towards proximally if the vibration iscoupled into the first object.

The first object and the connection to the second object may inembodiments be such as to seal the perforation off, i. e. to seal aregion proximally of the second object from a region distally thereof.To this end, the first object may for example have a continuous bodyextending to the periphery, which periphery embeds the edge.

In other embodiments, the first object has a through opening, in whichthrough opening for example a connector piece or not liquefiable body asdescribed hereinafter may be arranged, which piece or body forms ananchor piece for a further object. It may for example have a thread orother engagement feature, and/or it may serve for a nut-and-boltarrangement extending through it. Alternatively, a bearing sleeve, aball bearing or other bearing may be positioned in the first object,especially a through opening of it.

Especially, the mechanical vibration energy may be coupled into thefirst object and not (not directly, i.e. at most via the first object)into the second object. Especially, in the step of positioning, thefirst object may be brought into contact with the second object from agenerally proximal side, and the step of coupling energy into the firstobject may include pressing a vibrating sonotrode against a proximallyfacing coupling face of the first object, whereby by the sonotrodesimultaneously the pressing force relative to the second object andmechanical vibration are coupled into the first object.

For applying a counter force to the pressing force, the second objectmay then be placed against a support, for example a non-vibratingsupport. In embodiments, the second object is placed against a supportwith no elastic or yielding elements between the support and the secondobject, so that the support rigidly supports the second object.

However, the pressing forces applied during the process may be lowenough for the second object to be self-supporting. In general, theapproach according to the present invention given the generally verygood energy absorption characteristics of an edge (being an intrinsicenergy director for mechanical vibration energy) in physical contactwith a thermoplastic object, the thermoplastic object and/or the edgebeing subject to mechanical vibration, makes possible that only smallpressing forces have to be applied. This may be a substantial advantagefor applications in which at least one of the objects has a complexshape and/or is part of complex item, such as a car body, and wheretherefore placing a rigidly supporting support at the lateral positionwhere the pressing force is applied can be difficult.

It is not excluded, though, that the energy is coupled into the secondobject, i.e. the mechanical vibration energy impinges from the side ofthe second object.

Especially, but not only, embodiments that include coupling thevibration into the second object, the vibration may be transversevibration, whereas in other embodiments the vibration will belongitudinal vibration. Set-ups with transverse vibration are forexample known from welding of metallic parts. For this, for example thefollowing options exist:

-   -   A sonotrode couples vibration into the second object from a        generally lateral direction (in-plane direction with respect to        the sheet plane of the second object, if defined), whereas a        separate pressing tool applies the required pressing force        between the first and second objects.    -   A sonotrode itself is caused to be subject to transverse        vibration at the distal end where it is coupled to the second        object. To this end, a mechanical coupling between the sonotrode        and the second object may be such that such transverse movement        is capable of being transferred to the second object. For        example, the second object may in addition to an anchoring plate        including (for example constituting) the sheet portion also        include a fastening element that may be coupled to the        sonotrode. Especially, in embodiments the second object is a        fastener configured to fasten a further object to the first        object, and the fastening element has a corresponding structure,        for example by being a threaded bolt (inner and/or outer        thread), a bolt without a thread, a pin, a nut, a hook, an        eyelet, a base for a bayonet coupling, etc.

The present invention also concerns a set of a sonotrode and of a secondobject adapted thereto for carrying out the process according to anyembodiment of the invention that includes coupling the mechanicalvibration into the second object. For example, the second object mayinclude an anchoring plate and a fastening element bonded thereto, andthe sonotrode may include a distal outcoupling face shaped for a forceand vibration transmitting contact with the anchoring plate, and areceiving structure for accommodating the fastening element. Thereceiving structure, for example receiving opening or protrusion may beadapted for mechanical coupling to a fastening structure (thread orsimilar) of the fastening element.

Optionally, in addition to the mechanical vibration energy, furtherenergy may be coupled into the assembly. In an example, the secondobject may be pre-heated by IR irradiation, induction (especiallyefficient near the edge), a hot air stream, etc. In addition or as analternative, the thermoplastic material may be pre-heated locally nearthe interface to the edge, for example by electromagnetic heating asdescribed in Swiss patent application 01 104/15, by irradiation, etc.For example, for electromagnetic heating as described in Swiss patentapplication 01 104/15, the thermoplastic material in the attachment zonemay be provided with a magnetic dopant.

In both cases, the pre-heating assists the process of making thethermoplastic material flowable directly and/or indirectly. An indirecteffect is achieved if the pre-heating step causes the absorption ofmechanical vibration energy to be increased at/near the locations wherethe pre-heating step takes effect, especially due to enhanced internalfriction caused by the increased temperature.

Such additional, further energy may have the purpose of enhancing thevelocity and/or reducing the required pressing forces. This may alsohave a positive effect on the process control.

The flow portion of the thermoplastic material is the portion of thethermoplastic material that during the process and due to the effect ofthe mechanical vibration is caused to be liquefied and to flow. The flowportion does not have to be one-piece but may include parts separatefrom each other.

The liquefaction of the flow portion in this is primarily caused byfriction between a vibrating part of the assembly (such as the firstobject) and a non-vibrating part (such as the second object), whichfriction directly or indirectly heats the thermoplastic material of thefirst object. This is particularly efficient if the heat generatingfriction takes place at the place where the material is to flow, becausethen in contrast to other methods that include liquefied thermoplasticmaterial, the there is no cooling effect at places where the flowportion has flown away from the heat source. Especially, in the step ofcausing a flow portion of the thermoplastic material to become flowable,the flow portion or parts thereof may become flowable due to heatgenerated between the projecting section and the thermoplastic material.In embodiments, the second object by the above-described method steps issecured to the first object wherein a space on the other side of thesecond object than the side from which the first object is brought intocontact with it (a distal side in embodiments of the above-mentionedkind in which the vibration energy is coupled into the first object froma generally proximal side) may be free along the edge (thus, ifapplicable, around the perforation) so that the thermoplastic materialcan flow immediately along the surfaces of the second object's sheetportion. Especially, in embodiments no further object distally of thesecond object is secured to the second object by the first object.

In embodiments, the sheet portion along the edge (thus if applicablearound the perforation) is deformed so that the sheet portion projectsaway from a sheet plane defined. Especially, the sheet portion mayproject towards the side of the first object (towards the proximal sidein embodiments of the above-mentioned kind in which the vibration energyis coupled into the first object from a generally proximal side).Especially, the projecting section (if any) being a deformed section maybe of a same metal sheet material as the sheet portion.

In this text, the term “sheet plane” denotes the plane/surface definedby the shape of the generally planar sheet portion in a region aroundthe edge, especially around the perforation (if any). The sheet planemay be planar in the sense of extending straight into two dimensions.Alternatively, the sheet plane may be curved and thereby follow a morecomplex 3D shape, for example if it constitutes the surface of a complexobject, such as a body of a vehicle or aircraft. In case the secondobject is, near the edge, deformed to project away from the sheet plane,the curvature of second object at the location from where the deformedsection extends will often be much larger than the curvature of thesheet plane.

Such a deformed section may be formed by deforming a corresponding partof the sheet portion, for example by making a cut (for example bypunching) and bending or otherwise deforming hence leaving a secondelement opening where the corresponding part of the sheet portion hadinitially been. In this, the deformed section may still be one-piecewith the sheet section.

As an alternative to a deformed section, would also be possible toprovide a section of the sheet portion that projects away from the sheetplane as a separate element secured to the sheet material, for exampleby welding.

As an even further alternative to a deformed section, it would bepossible to manufacture a section projecting towards the side from whichthe first object is brought into contact, which section ends in theedge, by an ab-initio shaping process, such as by die casting orpressing or injection molding (followed by well-known subsequentprocessing steps) if the named section is of ceramic. In suchembodiments, the sheet portion may even consist of the portion thatprojects towards the first object and/or the section that after theprocess is embedded in the flow portion i.e. there is no need to have asheet plane that is further defined by the sheet portion.

In embodiments with a perforation and with a projecting (for exampledeformed) section around the perforation, the deformed section may besymmetrical, i.e. may be deformed uniformly around the perforation (thisincludes the possibility that the deformed section has a rough edge, forexample with a sawtooth-like shape). Especially, it may be symmetricalwith respect to rotation around an axis perpendicular to a sheet planethrough a center of the perforation.

Alternatively, it may be asymmetrical with respect to rotation aroundsaid axis in that the height (average height in case of a rough/toothededge) of the projecting section differs as a function of the positionalong the edge. In such embodiments, the asymmetry may even be such thatthe projecting section does not extend all around the perforation butalong some segment of the edge there is no such projecting section. Inthis case, however, the projecting section may extend around at leastmore than 180% of the periphery so as to lock the first and secondobjects with to each other with respect to all in-plane relative forces.

In a group of embodiments with the second object including a perforationalong which the edge runs, the sonotrode and the first object may beadapted to each other so that the coupling face (the part of the firstobject surface against which the sonotrode is pressed) covers in-planepositions of the edge but does not extend to a central position withrespect to the perforation. “To cover in-plane positions” in thiscontext means that in a projection along the proximodistal axis the edgelies in an area of the coupling face.

For example, the coupling face may form a lane around a center, with anin-plane position of the center corresponding to an in-plane position ofthe perforation.

To this end, either one or a combination of the following options may berealized:

-   -   The sonotrode includes a central indentation, with the coupling        face around the central indentation; and/or    -   The first object includes a proximally facing central        indentation, with the coupling face around the central        indentation.

Effects of the coupling face not extending to central positions mayinclude making process control easier, and/or preventing centralportions of the first object, for example having a functional element,from becoming damaged.

In a group of embodiments that include the perforation of the secondobject and a projecting section around the perforation, the projectingsection projecting towards proximally towards the first object, thefirst object may be provided with a distally facing spacer (alsoreferred to as “foot portion” in this text). Such spacer may be arrangedlaterally of the location where the first object's contact side comesinto contact with the edge of the second object.

Especially, the spacer may be arranged more laterally than theprojecting section of the second object, whereby, when the first andsecond objects are pressed against each other when the vibrationimpinges, a relative movement of the first and second objects againsteach other can be caused until the foot portion abuts against the sheetportion where the sheet plane is defined. Thereby, the z-position of thefirst object relative to the second object is defined by the dimensionof the foot portion that serves as a spacer.

Such a foot portion, therefore, is an example of a relatively simplemeasure for achieving z position control without sophisticatedmeasurement tools. Especially, the foot portion makes a good processcontrol possible in that at the end of the process the operator has aphysical feedback when he has reached the right z position. This may beadvantageous if the process is carried out manually or also if themechanical resistance is a control parameter in an automated process.Other measures for precise z position control are discussed hereinafter.

The method may include the further step of manufacturing a perforationin the second object prior to the step of positioning, for example bypunching, drilling, etc. Alternatively, the perforation along which theedge is formed in embodiments may be an opening that exists in thesecond object anyway or has been provided in a manufacturing process.

The first object includes thermoplastic material. In embodiments, thefirst object consists of thermoplastic material. In other embodiments,the first object in addition to the thermoplastic material includes abody of a not liquefiable material. Such a body of not liquefiablematerial may constitute a reinforcer portion of the first object.

In embodiments with a not liquefiable body, the body of the notliquefiable material is different from a mere filler of a large numberof particles but is a macroscopic body with a defined position andorientation and of a substantial size. In a sheet plane defined by thesecond object, the size may be for example at least 10% of first objectaverage diameter (of a cross section perpendicular to the insertionaxis) or, if applicable, of a perforation average diameter, and/or acharacteristic dimension may be at least 0.1 mm in any dimension.Especially, the body may be metallic or of ceramics. Especially, thebody may be such as to have a defined shape and to thereby add stiffnessto the first object. By the body, the first object is defined into atleast two spatially separated regions, namely the body region and thethermoplastic region.

In embodiments in which the first object in addition to thethermoplastic material includes not liquefiable material, thethermoplastic material may be arranged at least on surface portions thatcome into contact with the edge.

The first object may include a fixation element for fastening a furtherobject to the second object. For example, the first object may itself besuch a fixation element (fastener) by including an appropriatestructure, such as a thread or other fastening structure, or it maycarry a dedicated fixation element, such as a threaded bar, nut, etc. Inthese embodiments, the first object may be viewed as a fastener—oranchor—for the further object. In alternative embodiments, the firstobject may itself constitute an object having a function different frombeing a mere fastener.

Especially, but not only, in these alternative embodiments, the firstobject may be relatively large, it not being possible to vibrate thewhole first object to attach the first object simultaneously at aplurality of attachment locations. In such embodiments, it may be eithernecessary to simultaneously cause a plurality of sonotrodes to impingeto attach secure the first object to the second object at acorresponding plurality of attachment locations, and/or it maybeneficial to have sufficient flexibility to sufficiently de-couple theportion of the first object where attachment takes place from a rest ofthe first object. Examples for this are discussed hereinafter, forexample referring to the attachment flange.

In embodiments, the first object has an attachment zone that includesthe thermoplastic portion and further has a functional zone differentfrom the attachment zone. Such functional zone may for example includethe fastening structure and/or other functional elements. The functionalzone may be configured so that it is not possible and/or not desired tolocally liquefy thermoplastic material that will embed the edge in theprocess. In many embodiments, the first object in the functional zone isnot liquefiable. In other embodiments, the first object in thefunctional zone may include liquefiable material, however, the functionwould be adversely affected by the process according to the invention.

In embodiments, the first object is manufactured in a process thatincludes a step of two-component injection moulding, with the attachmentzone being of one thermoplastic material and the functional zoneincluding another thermoplastic material. Then (or also in othersituations with the first object including two thermoplastic materialparts), the thermoplastic materials of the different zones havedifferent material properties.

-   -   The modulus of elasticity E of the thermoplastic material of the        functional zone may be greater, for example much greater, than        the according modulus of the attachment zone; and/or    -   The (elastic) extensibility of the thermoplastic material of the        attachment zone may be much higher than the extensibility of the        functional zone. To this end, the thermoplastic material of the        attachment zone may optionally be an elastomeric thermoplastic        material, such as thermoplastic polyurethane. Thereby, it is        suited for repeated heating/cooling cycles. According to another        option, the thermoplastic material of the attachment zone may be        a partially crystalline polymer with a relatively low glass        transition temperature and a comparably high plasticity at        elevated temperature (for example polypropylene) to compensate a        thermic distortion, for example in an electrodeposition process,        by a one-time plastic deformation (creeping) process.

By the latter, for example different thermal expansion behaviors betweenthe first object and the second objects may be compensated for.

In embodiments that include at least one attachment zone, the materialof the attachment zone(s) may be secured to a first object body (thatincludes the functional zone(s)) by a positive-fit connection. Forexample, the first object body may include at least one undercutopening, and the thermoplastic material forming the attachment zone(s)may be present at least partially in the undercut opening(s). Inaddition or as an alternative, the body may include an open poroussection, with the thermoplastic material of the attachment zone(s)interpenetrating the porous section. In addition or as an alternative tothe positive-fit connection, also other kinds of mechanical connectionsbetween the material of the attachment zone and the body may be present,such as an adhesive connection.

In a group of embodiments, the first object includes a body that definesthe functional zone and a flange (attachment flange) running along atleast a portion of a lateral periphery of the body and defining theattachment zone, whereby at least portions of the flange in the step ofcoupling mechanical vibration energy into the assembly are clampedbetween a sonotrode acting in an axial direction and the second object.

An attachment flange may be a peripheral, laterally protruding portionof the first object. It may consist of the thermoplastic material; atleast a distal face includes the thermoplastic material. It may forexample define a proximally facing incoupling surface for a sonotrodethat is at least approximately parallel to the distal surface of thefirst object where the latter is in contact with the edge of the secondobject 2. Thereby, even if the first object due to its function has acomplex shape that may be different from a shape having a plane distalsurface, a less complex shape at the attachment location(s) becomespossible.

The first object, especially an attachment flange thereof, may include awell-defined, possibly marked proximally facing coupling surface portionthat is positioned to correspond to an attachment location defined bythe second object, for example a perforation thereof, along which theedge extends. Such coupling surface portion may for example be parallelto the corresponding distally facing surface portion on the oppositeside, which comes into contact with the edge of the second object.

Also, the first object may include an elastic joint between anattachment flange—or other attachment structure that has the couplingsurface and the surface portion that comes into contact with theedge—and a first object body. Thereby, the attachment structure, forexample attachment flange—can be vibrationally de-coupled from the restof the first object.

This may especially be an option in embodiments in which the firstobject is comparably large and in which it is not readily possible tocouple vibration into the whole first object or in which it would bedetrimental do to so. In such embodiments, attachment at differentattachment locations either has to be carried out simultaneously formany attachment locations, in which case several sonotrodes have to actsimultaneously. An alternative is sequential attachment at differentattachment locations. Then, there is the need of a certain flexibilityof the first and/or second object, since the attachment process bringsabout a relative movement of the first and second objects at the actualattachment location, whereas such movement is not present at otherattachment locations. An attachment flange and/or an attachmentstructure separated from the body by a joint may bring such flexibility.

In a group of embodiments, the method includes the further step ofproviding a connector piece that is initially separate from both, thefirst and the second objects. In these embodiments, the assembly intowhich the mechanical vibration energy is coupled also includes theconnector piece. The connector piece in the process may be caused to beembedded at least partially in thermoplastic material of the firstobject and to be, after re-solidification, anchored with respect to thefirst and second objects. In embodiments, as described in more detailhereinafter, a connector piece may be connectable (by being embedded orby another connection) to the first object in a plurality of possiblerelative positions, for example to compensate for variations ofdimensions/positions during a manufacturing process.

Especially, in the step of coupling mechanical vibration energy into theassembly, a vibrating sonotrode may be pressed against a coupling faceof the connector piece while the connector piece is pressed against thefirst object until the thermoplastic material of the first objectbecomes flowable in a vicinity of the connector piece so that theconnector piece is driven into the first object. Simultaneously and/orsubsequently, mechanical vibration energy may also be absorbed at theinterface between the second object and the first object.

The connector piece in this may be caused to extend through a planedefined by the edge of the sheet portion, thus if applicable by a mouthof the perforation, from a proximal side thereof. Similarly, in case thefirst object has a body of a not liquefiable material, such as areinforcer portion, the body may be arranged to extend through the planedefined by the edge (if applicable the mouth of the perforation). Morein particular, in embodiments in which the second object has aperforation, the connector piece/the body may extend through theperforation.

A connector piece of the discussed kind may consist of a not liquefiablematerial. Alternatively, it may include a thermoplastic material. In anexample, it includes a thermoplastic material that is capable of beingwelded to the thermoplastic material of the first object; it may be of asame thermoplastic material or at least include a same matrix polymermaterial.

A connector piece of the discussed kind may have one or a combination ofthe following functions:

-   -   The connector piece may form together with thermoplastic        material an interface at which absorption of mechanical energy        takes place. Thus, the connector piece provides an additional        means to control the energy absorption and thereby the flow of        the thermoplastic material.    -   The connector piece may be shaped to confine the flow of the        thermoplastic material, especially inwardly with respect to        radial direction, thereby causing the material to more        pronouncedly flow around the second object near the edge,        especially on its distal side.

The connector piece may have further functional elements, such as aconnecting portion, flange, etc. Generally, the considerations in thistext that apply to the shape and function of the connector piece alsoapply to a body of not liquefiable material that is part of the firstobject (such a body could be viewed as pre-mounted connector piece).

A body of not liquefiable material of the first object or a connectorpiece may carry structures serving for further functions, such as athread, another mechanical connection, a contact or feedthrough, etc.

Independent of whether there is a body or a connector piece or not, in agroup of embodiments, the method includes attaching a first object to ametal part that forms part of a car body.

In embodiments, the body or connector piece, respectively, has a surfacewith at least one retaining feature on a lateral surface part, whichretaining feature cooperates with thermoplastic material the body tostabilize the relative position of the body, within embeddingthermoplastic material.

The present invention also concerns a connector piece having theproperties as defined in this text. The invention further concerns a kitof at least one connector piece and a first object and/or a sonotrode.

The invention moreover concerns a connector that is a first objectaccording to any embodiment described in this text or of which such afirst object forms part. The invention moreover concerns a fastener thatis a second object described in this text and includes a fasteningelement.

In a group of embodiments, the first object includes a structuredcontact side that includes the thermoplastic material. The contact sideis the side of the first object that is brought into contact with edgefor the securing. The fact that the contact side is structured meansthat it is different from just being flat and even and that it includesprotrusions/indentations. For example, it may include a pattern ofridges and grooves, for example a regular pattern.

It has been found that a structured contact side may have the effect ofreducing the energy and force inputs required until the edge haspenetrated into thermoplastic material of the first object to asufficient depth. Especially, this required input may be reduced by morethan just a proportionality factor corresponding to the portion ofunfilled volumes of indentations. This may be attributed to additionalflow channels being generated by the structure.

In an embodiment, the structure forms a pattern of radially extendingridges/grooves.

In embodiments in which the sheet portion of the second object has aprotruding section projecting away from the sheet plane towards thecontact side, the depth of the indentations may be chosen to be smallerthan a height of the protruding section.

A further group of embodiments also addresses the issue of reducing therequired force and/or energy input. In this further group ofembodiments, the second object includes a plurality of for examplesmaller peripheral perforations arranged around a for example largermain perforation.

Such peripheral perforations may especially be arranged in a section ofthe second object that projects away towards the contact side from asecond object sheet plane, i.e. the peripheral perforations may bearranged where the sheet material is sloped with respect to the sheetplane.

Such peripheral perforations have the effects of enhancing the footprintof the connection, of providing an additional securing against rotation,and of reducing the resistance during the process by providing furtherflow channels.

Referring to the hereinbefore discussed groups of embodiments, areduction of the energy and force input may be desired especially if theinvolved materials are delicate and/or if the method is applied at arelatively advanced stage of manufacturing a complex article. Forexample, in embodiments the second object may include alacquered/painted piece of sheet metal, and the lacquer/paint may bedamageable. The approach according to these groups in such situationsmay be advantageous.

In many embodiments, if the method includes pressing the first objectagainst the second object while vibration is coupled especially into thefirst object, a counter force to the pressing force is generated by thesecond object being held at a position different from the locationagainst which the first object is pressed, such as a mounting frame orby the second object being part of a complex, comparably heavy item thatstands on a ground. Then, consequently, the counter force relies on thestiffness of the second object. If needed, a dedicated support may beused to assist.

In a group of embodiments, in addition to the second object a dedicatedanvil structure is used. An anvil of such structure may be placeddistally of the second object, and it may have at least one of thefollowing functions:

-   -   The anvil directs the flow of flowable thermoplastic material        and consolidates. Thereby, the overall stability of the        connection between the first and second objects after the        process is enhanced, and this ultimately reduces the required        penetration depth. Thus, also use of an anvil may be a measure        for reducing the required force and energy input.    -   The anvil may also support the second object and avoid undesired        deformation thereof, if for example the second object is        comparably thin or weak.

Such anvil may be different from merely flat. Especially, it may includea directing protrusion outside of the edge (inward with respect to thecenter of the perforation if the edge extends along a perforation) andan indentation distally of the edge (and radially outward from the edgeif the edge extends along a perforation) to direct a flow to“underneath” (distally of) the edge and the second object portionsadjacent the edge.

A volume of such indentation may especially be smaller than a volume ofthe thermoplastic material available for becoming flowable, so that ifthe vibration input is maintained sufficiently long, a volume of theflow portion is higher than a volume of the indentation. Thereby, asufficient shaping pressure may be built up during the process, wherebythe filling of the indentation by the flow portion is controlled andpredictable.

In a group of embodiments, the method includes adjusting a position ofthe first object and/or of a sonotrode relative to the second object.This especially pertains to an x-y (in-plane) position. For this, twobasic configurations exist:

-   -   In a first basic configuration, the x-y-position of the        sonotrode with respect to the second object is defined, for        example by a mounting frame, and the step of adjusting includes        adjusting a position of the first object that is arranged        between the sonotrode and the second object, with respect to the        sonotrode and the second object.    -   In a second basic configuration, one uses means for defining a        position of the first object relative to the sonotrode, and the        step of adjusting includes adjusting a position of the        first-object-sonotrode assembly relative to the second object.

In accordance with the first basic configuration, the means by which theposition of the first object is adjusted relative to the sonotrode andthe second object (holders or similar) are by construction independentof the sonotrode. Then, one has to ensure that the mechanical vibrationscan be coupled into the first object. To this end, according to a firstoption, the shape of a guiding tool used for this is adapted to theshape of the first object in a manner that only the transversal positionis precisely defined but that there is some degree of freedom withrespect to movements in axial directions (for longitudinal vibrationcoupled into the first object). According to a second option, that canbe combined with the first option, the guiding tool includes a spring sothat the first object is only loosely coupled to any mounting frame.

In accordance with the second basic configuration, the sonotrode and thefirst object may be adapted to each other for the lateral relativeposition being defined. For example:

-   -   The sonotrode may include a guiding protrusion cooperating with        a guiding indentation of the first object, or vice versa.        Optionally, such guiding protrusion/guiding indentation (or        other guiding means) may be different from rotationally        symmetrical to prevent any rotation of the first object relative        to the sonotrode.    -   The sonotrode may include a peripheral flange encompassing the        first object to define its position.    -   The sonotrode may include at least one penetrating guiding        element (spike or similar) that during the process penetrates        into material of the first object.    -   It would also be possible to secure the first object temporarily        to the sonotrode, for example by screwing or similar.

In addition or as an alternative, other means may be used to temporarilycouple the first object to the sonotrode, for example a vacuum beingapplied between the sonotrode and the first object, for example throughsuction channels through the sonotrode.

In addition or as yet another alternative, a separate guiding elementmay be used. Such separate guiding element may be laterally guided both,relative to the sonotrode and relative to the first object. Especially,it may be guided relatively loosely relative to the sonotrode so thatthe vibration is not coupled into the guiding means. Such guidingelement may be a cylindrical element guided in aligned openings thefirst object and the sonotrode, the openings adapted to a cross sectionof the guiding element. Especially in embodiments in which the guidingelement is loosely guided also relative to the first object, anadditional axial support may be provided for preventing the guidingelement from breaking loose from the assembly.

If applicable, the cylindrical shape of such guiding element may butdoes not need to be the shape of a rotational cylinder.

In addition or as an even further alternative, a hold-down tool that isdifferent from the sonotrode and used in addition thereto, is used. Suchhold-down tool is used to press the first object against the secondobject at least during an initial phase of the step of couplingmechanical vibration energy into the assembly. By such hold-down toolthe issue is addressed that when longitudinal vibration is coupled froma sonotrode into a first object, wherein the sonotrode is pressedagainst the first object, during about a half-wave per oscillationcycle, the sonotrode does not exert any force on the first object.Absent any lateral guidance (for example as described above), this maycause a loss of control, with the first object “floating” relative tothe second object. An additional hold-down tool ensures that the firstobject is pressed against the second object. Such additional hold-downtool may include a guiding structure defining a lateral position of thefirst object relative to the guiding tool, for example a peripheralflange.

The approach according to the invention features the substantialadvantage that the attachment location defined by the edge that in theprocess is embedded in the flow portion does not have a preciselydefined position, even if a precise positioning of the first object withrespect to the second object is desired and achieved.

More in concrete, for the variation of the relative positions of theattachment location and of the first object, the following statementsmay be made:

-   -   The lateral (x-y) variation largely depends on the lateral        extension of the first object or of an attachment zone thereof,        respectively. For relatively small attachment zones (for example        small perforation, they may for example be between 0.1 mm and        5 mm. For larger attachment zones (for example a larger        perforation), they may scale to higher figures.    -   The axial (z-) variation if the first object has a flat distally        facing surface depends on how far the section of the second        object protrudes towards the first object. It may vary between        0.1 mm and 2 mm for relatively small heights of the protruding        section any may be higher for larger dimensions.    -   Depending on how far apart different attachment locations are,        or more generally on the lateral extension of the attachment        zone, an angle variation of up to 10°-20° may be compensated.    -   In many embodiments, a restriction is given in that around the        attachment zone thermoplastic portions not belonging to the flow        portion should remain. A thickness of this non-liquefied zone        for example may be at least 1 mm in all dimensions.

Due to this effect, the approach according to the invention may be usedfor tolerance compensation, for example by the following method:

-   Step 1: measuring the tolerance mismatch, for example by optical    methods and comparison with CAD data.-   Step 2: calculating the position correction x,y,z, angle.-   Step 3: Positioning the first object and the second object with    respect to each other in the calculated corrected position x,y,z,    angle (minus a z-offset accounting for a relative movement of the    first and second objects during the subsequent step 4).-   Step 4: Performing the method according to any concept and/or    embodiment described in this text, until the correct calculated    position has been reached.

Optionally, there may be correction accounting for the softness of thestructure by an external distance measuring system coupled to the deviceby which the vibration energy is applied, which correction system adaptsthe end z-position if necessary.

In embodiments, in addition or as an alternative to this, anothermeasure for compensating for z-variations may be taken. By this othermeasure, the above-named range of z-variations (of for example between0.1 mm and 2 mm) may for example be outdone, also this measure makesdifferent kinds of control over the z variation compensation possible.

This other measure comprises:

-   -   Providing an anchoring part and an adjustment part, wherein at        least the anchoring part belongs to the first object (and in        embodiments may be constituted by the first object).    -   Adjusting a z-position of the adjustment part with respect to        the anchoring part; and    -   Fixing the adjustment part with respect to the anchoring part        while it is in the adjusted position.

The z-direction may be a direction perpendicular to a sheet planedefined by the second object in a vicinity of the attachment location.Alternatively, for example if such plane is not defined, the z-axis maybe defined to be the axis along which the pressing force acts during thestep of applying the mechanical vibration for causing the edge to beembedded.

The following options may apply:

-   -   The step of fixing may cause a non-releasable fixation of the        adjustment part with respect to the anchoring part. For example,        the step of fixing and/or the step of adjusting may include        impinging the assembly of the anchoring part and the adjustment        part with mechanical vibration to cause thermoplastic material        of at least one of the parts to become flowable and to fix,        after re-solidification the parts to each other.        -   Such fixing the parts to each other after re-solidification            may according to a first option be caused by material of the            objects fusing together, for example in a weld, or            alternatively because the anchoring part and the adjustment            part are of one piece, with a transition zone (collapse            zone, expansible zone) between them that is deformable when            the thermoplastic material is flowable (in this, flowable            includes “pasty; plastically deformable by moderate force            input”).        -   According to a second option, the parts may be fixed to each            other in that one of the parts includes liquefiable material            (especially thermoplastic material) and the other one            includes structures capable of being interpenetrated by the            liquefiable material, whereby after re-solidification a            positive-fit connection between the parts is achieved.        -   In addition or as yet another alternative, the parts may be            fixed to each other by an adhesive connection between            re-solidified material and other material it adheres to.    -   The steps of adjusting and of fixing may be combined in a        single-step procedure. For example, they may be carried out by a        vibrating sonotrode pressing the parts against each other and,        after material has become flowable, moving the parts relative to        each other until a desired z-position has been reached,        whereupon the movement and the energy input are stopped        (depending on the configuration, the energy input may be stopped        already some time before the desired position has been reached).        After re-solidification, the re-solidified flowable material        fixes the relative position. Optionally, during        re-solidification, a holding force may be maintained.    -   As an alternative, the step of adjusting may be carried out        prior to the step of fixing. Then, for embodiments that include        fixing by input of mechanical vibration energy, the anchoring        part and the adjustment part may be equipped for their relative        z-position being provisionally locked so that the joint action        of mechanical vibration and a pressing force does not alter the        relative z-positions. For example, the anchoring part and the        adjustment part may have threaded portions cooperating so that        the adjustment part can be screwed on the anchoring part. Other        configurations for such provisional locking are possible. As an        alternative to such provisional locking, the mechanical        vibration may be coupled into the parts from a direction not        parallel to the z-axis but for example essentially perpendicular        thereto.        -   For example, initially measurement data concerning            particulars of the second object (or an assembly that            includes the second object) and/or particulars of any other            part (first object, other object to be secured to the first            object) may be obtained. Based on this, the desired            z-adjustment may be calculated in advance.        -   The alternative of adjusting prior to fixing may be used for            separating the steps in a manufacturing process. A            manufacturing line then includes an adjustment station and a            fixing (securing) station. Especially, if the second object            is comparably large or belongs to a comparably large            pre-assembly (for example a vehicle body), this may be            advantageous because then the z-adjustment step may be            carried out at a much smaller station and does not delay the            main process.    -   The adjustment part may be a connector piece or a body of the        above-described kind.    -   Alternatively, the anchoring part may include a connector piece        or a body of the above-described kind, and the adjustment part        may optionally be a further item that is equipped to be fixed        relative to the connector piece/body in an adjustable position.    -   According to a further alternative, the adjustment part and the        anchoring part both include thermoplastic material, and the        adjustment part and the anchoring part are weldable to each        other.    -   As yet another alternative, the anchoring part and the        adjustment part are one-piece, but with a collapse zone or        stretching zone between them, this zone being activatable by the        energy input.    -   If the anchoring part and the adjustment part are not one-piece,        the method may include positioning the adjustment part relative        to the anchoring part prior to the step of adjusting.    -   The step of adjusting may be carried out after the step of        securing the first object to the second object and/or may be        carried out simultaneously

These possibilities can be arbitrarily combined unless stated otherwise.

In embodiments that include fixing and/or adjusting by mechanicalvibration energy input, the fixing and-or adjusting may according to afirst option be carried out together with securing the first object tothe second object. Alternatively, fixing and/or adjusting the parts withrespect to each other may be carried out after securing. As an evenfurther alternative, as mentioned hereinbefore and as discussed in somemore detail hereinafter, fixing and/or adjusting the parts with respectto each other may be carried out prior to securing.

In either case optionally both, the step of coupling mechanicalvibration energy into the assembly to embed the edge of the secondobject for securing, and the step of coupling mechanical vibrationenergy into the assembly for fixing and/or adjusting may includepressing a vibrating sonotrode against the assembly along a directionthat is not perpendicular to the z-axis but for example along adirection parallel to the z axis or at a certain angle thereto.

In a first sub-group implementing this option, the pressing forcesapplied for securing and for fixing/adjusting have same directions. In asecond sub-group, they have opposed directions.

In either case, in the step of coupling energy into the assembly andpressing a vibrating sonotrode against a coupling face for securing thefirst object to the second object, a portion of the second object maydefine a stop face for a movement of the first object relative to thesecond object during securing. After the first object has gotten incontact with the stop face, the mechanical resistance against a furthermovement raises drastically. Thereby, the relative positions of thefirst object and the second object are defined, and when subsequently apressing force and mechanical vibration are coupled into the assemblyfor fixing and/or adjusting, the relative position of the first objectand the second object will remain defined.

Such a stop face may for example be defined by a flat part of the secondobject around the attachment location/attachment locations.

The above-described approach of adjusting and fixing in the adjustedposition may be implemented in embodiments of the herein describedaspect of the invention. It may, however, also be implementedindependent thereof.

The invention also concerns a device that includes an anchoring part andan adjustment part according as described referring to any embodiment ofa method mentioned in the present text.

In a group of embodiments, with or without a step of adjusting az-position, the second object includes an extension opening (that isdifferent from a perforation along which the edge that is caused to beembedded in the thermoplastic material extends). The first object(and/or a connector piece secured thereto) then may extend through themouth of the opening. Thereby, there is more space and especially moredepth available for functional parts of the first object and/or theconnector piece, respectively.

The second object does not need to project towards the side of the firstobject along the extension opening and does not need to have any othershape that is specifically adapted for a fixing/securing step. Also,because of the space available due to the extension opening, thedimensions of the functional parts/connector piece may be chosen

In embodiments of this group, the first object has an extending portionextending through the mouth of the extension opening.

A connector piece may be equipped to also extend through the mouth ofthe opening and to be secured relative to such extending portion.Especially, the connector piece may be capable of being secured indifferent depths, whereby it is an adjustment part with an adjustable zposition in the above sense. Also, it is not necessary that a movementby which the connector piece is inserted into the extending portion iscollinear with the movement during securing, so that adjusting the zposition includes adjusting a z′-position with the z′ axis being at anangle to the z axis. All in all, the parameters applicable for fixingthe connector piece relative to the first object become independent ofthe securing process due to the extension opening.

In some embodiments that include an extension opening and a connectorpiece, the connector piece is equipped for a further object to besecured thereto. To this end, a joining element may be provided tosecure the further object, especially if the further object has arelatively large extension in two in-plane dimensions. For example, insuch embodiments, the further object may be clamped between headportions of the connector piece and the joining element.

A joining element of this kind may for example be capable of beingclipped or screwed onto the connector piece or secured by a bayonetcoupling like connection, or of being secured thereto by a materialconnection (adhesive connection, soldered connection, weld, etc.)

Also, in embodiments of this group, a size of the extension opening islarger than at least one in-plane dimension of the extending portion,whereby an x-y-position of the functional parts and/or connectorrelative to the second object becomes possible.

In embodiments, an extending portion includes a tube portion extendinginto the opening, whereby a connector piece can be placed at leastpartially in the tube portion.

Embodiments of the second object that include the extension opening mayinclude a plurality of perforations of the above-discussed kind,especially perforations around which the second object has a sectionprojecting towards the side of the first object (proximal side if thevibration is coupled into the first object, distal side if the vibrationis coupled into the second object). Such perforations may especially bedistributed around a periphery of the extension opening.

In such embodiments or other embodiments with a plurality of theperforations, the first object may especially be of the type includingan attachment zone (for example an attachment zone per perforation) anda functional zone. Especially, the first object may be of adimensionally stable material, for example a metal, a composite,ceramic, etc., with the exception of the attachment zone(s) that includethe thermoplastic material.

Embodiments that include an extension opening are especially suited forset-ups in which the second object, the first object and/or, ifapplicable, the further object is not planar in the sense of extendingstraight into two dimensions but has a complex 3D shape. This is becausethe extension opening provides an additional degree of freedom for aconnection—especially using the connector piece—that may extend intospaces and into directions that are not restricted by the geometry ofthe locations where the fastening takes place, for example aroundperforations of the kind described in this text.

In alternative embodiments, if the dimensions allow so, the first objectmay have an extending portion that extends into the perforation of thesecond object and through the sheet plane (if defined). Then, a separateextension opening may not be necessary. Also in these embodiments, theextending portion of the first object may have an attachment structurefor securing a further object. Such attachment structure may include athread, a bayonet fitting-like structures, a glue channel, a region ofductile material for a self-tapping screw to engage, etc.

Embodiments of the present methods and applications of the devicesdescribed in this text include a combination of the securing approachdescribe herein with the use of an adhesive.

Especially, if two objects are fastened to each other by an adhesive,often the waiting time until the adhesive connection is sufficientlystrong and the lack of stability of the connection therebefore is anissue. This issue is even more severe if the adhesive connection andhence the thickness of an applied adhesive portion have to be comparablythick for example so that the connection exhibits a residual flexibilitynecessary for compensating different thermal expansion behaviours ifnecessary. Similarly, thick layers of adhesive are in many situationsnecessary if the adhesive has the additional function of sealing. Oftenone- or two-component Polyurethane adhesives are used for such purposes.

-   -   In accordance with a first option, therefore, a combination of        the securing approach according to the invention with applying        an adhesive may include positioning the objects to be connected,        applying an adhesive (prior or after the positioning) and        securing the objects to each other by the securing method        described in this text.    -   In accordance with a second option, a portion of an adhesive is        used as a sealant in addition to the mechanical connection        caused by the securing approach described in this text.

According to an other aspect, a method of providing an anchor in adesired x-y-z position relative to a second object is provided, themethod including the steps of:

-   -   Providing a first object including a thermoplastic material in a        solid state;    -   Providing the second object including an attachment location,        the attachment location including an edge of a not liquefiable        material;    -   Positioning the first object relative to the second object to        provide an assembly including the first and second object, in        which assembly the attachment location is in contact with the        thermoplastic material;    -   While the attachment location is in contact with the        thermoplastic material, coupling mechanical vibration energy        into the assembly until a flow portion of the thermoplastic        material becomes flowable and least partially embeds the edge in        the thermoplastic material;    -   Stopping the mechanical vibration and causing the thermoplastic        material to re-solidify, whereby the re-solidified thermoplastic        material at least partially embedding the edge anchors the first        object in the second object,    -   providing an anchor piece equipped for anchoring a further        object with respect to the second object,    -   Adjusting a position of the anchor piece with respect to a body        of the first object; and    -   Fixing the anchor piece with respect to the body of the first        object while it is in the adjusted position.

In this, the anchor piece may be an adjustment part of theabove-described kind. The body of the first object (first object body)may be the first object, or a part thereof that is fixedly secured tothe second object.

The above-discussed options for securing a first object to a secondobject as well as for adjusting a position of an adjustment part applyalso for this aspect.

Especially, the step of fixing and/or the step of adjusting may includeimpinging an assembly of the anchor piece and the body of the firstobject with mechanical vibration to cause thermoplastic material of atthe first object body or the anchor piece or both to become flowable andto fix, after re-solidification the anchor piece and the first objectbody to each other.

The invention also concerns a use of a method as described and claimedin this text for attaching a first and a second object to each other,wherein the second object has a at least one attachment location,especially a plurality of attachment locations, constituted by a (forexample deformed) portion defining the edge and projecting towards thefirst object, wherein a first tolerance for the positioning of theattachment location on the second object is greater than a secondtolerance corresponding to a tolerance for the final positioning of thefirst object with respect to the second object.

The invention even further concerns a method of mass producing aplurality of assemblies, each assembly including a first object securedto a second object, wherein the second object includes at least oneattachment location, wherein a standard deviation of the position of theattachment location between the different assemblies is greater than astandard deviation of the position of the objects with respect to eachother (and/or the position of one of the objects with respect to a thirdobject to which the other object is secured) between the differentassemblies (the standard deviation with respect to a respective averagevalue).

A further group of embodiments concerns the reversible fastening of afurther object to the second object by means of the first object.“Reversible fastening” in this context means that the further object canbe fastened to the second object and removed therefrom a plurality oftimes without any irreversible operation (such as breaking, melting,etc.).

More in particular, a further object is provided including at least oneconnector portion for removably connecting a first object to it, forexample by a clip-on connection. The method according to this embodimentincludes securing the first object to the second object by the methoddescribed in this text.

In a special sub-group of this group, where the approach of theinvention has particular advantages, concerns the situation where thefurther object has a plurality of connector portions for being fastenedto the second object at a plurality of locations. In accordance with theprior art, a plurality of fixing connectors for a releasable clipconnection had to be attached to the object with the flat surface (thesecond object in the terminology of the present text), at placescorresponding to the positions of the corresponding connector portion ofthe removable other object. The challenge in this is that for the clipconnection to properly work the positioning of the fixing connectorportions has to be very precise. This requirement is in practice ratherhard to be met in cost-efficient manufacturing.

In the embodiments of the here-discussed sub-group, this problem issolved by providing for every fastening location a first object. Thefirst object or, if applicable, a connector piece of the hereinbeforediscussed kind, is secured, by the reversible connection, to thecorresponding connector portion of the further object. A correspondingnumber of perforations of the second object at positions thatapproximately correspond to the positions of the first object areprovided. The process described in this text is then carried out forevery one of the first object while the first object or connector pieceis fastened to the respective connector portion. If the material of theinvolved objects is flexible enough, this may be done one by one foreach first object. Alternatively, all or some of the first objects maybe secured to the second object simultaneously.

The relative positioning of the first object and of the perforations ofthe second object in this need not be very precise and can, withoutadversely affecting the securing, vary within tolerances that are givenby the dimensions of the first object relative to the dimensions of theperforations. Thus, the tolerances for the positioning of the fasteninglocations (the perforations and deformed sections) with respect to thepositions of the connector portions of the further object are much morerelaxed than for prior art methods. Nevertheless, the positions of thereleasable clip-on connection are fixed precisely due to the fact thatthe first objects (or the connector pieces) are attached to the furtherobject during the securing process.

In another group of embodiments, the first object serves as connectorfor securing a third object to the second object, especially insituations where the third object like the second object has a flatportion and where the assembly of the second and third objects isaccessible only from one side. For example, the second and third objectsmay be metal objects, or fiber composite objects, or one of them may bea fiber composite object and the other one a metal object. Especially,the second and third objects may be of different materials havingsubstantially different coefficients of thermal expansion α.

According to the prior art, such connections were primarily achieved byblind rivets or by gluing. Blind rivets are technically rather complex.Further, both, blind rivets and glue connections feature the substantialdisadvantage that they have a very limited suitability to compensate forshear loads that arise if the objects connected react differently totemperature changes due to different coefficients of thermal expansion.For example, the coefficient of thermal expansion of Aluminium isα_(Al)=2*10⁻⁵ K, whereas the coefficient of thermal expansion of atypical CFK (carbon fiber reinforced composite) may even have theopposite sign: α_(CFK)=−5*10⁻⁶ K. For example, in industrialmanufacturing processes sub-assemblies after the assembly process oftenundergo a cathodic electrodeposition (or other immersion bath) process,which will take place at an elevated temperature of for example about180° C. For this reason, in industrial manufacturing, objects that afterbeing assembled with each other are subject to an electrodepositionprocess will in addition to be bonded by an adhesive connection also besecured to each other by a (blind) rivet. When subject to temperaturechanges, for example during the electrodeposition process (ifapplicable) or during use in varying environmental conditions, this willlead to deformation around the rivet connection, and hence to permanentinternal stress and/or bearing stress, depending on the set-up also todelamination, etc.

The approach according to the present invention provides a solution tothis problem.

To this end, the second object is arranged distally of the third object,and the third object is provided with a through opening, especially athrough opening having a larger diameter than the perforation of thesecond object along which the edge is formed. The step of positioningthe first object relative to the second object includes causing a distalportion of the first object to reach through the third object throughopening until the edge is in contact with the thermoplastic material.After the step of coupling the vibration energy into the assembly, thethermoplastic material by having flown around the edge will haveportions distally of the second object, which portions afterre-solidification may be viewed as forming a foot portion of the firstobject, which first object by this becomes a blind rivet.

In addition, in embodiments in which both, the second and third objectshave a defined attachment location, the requirements in terms ofpositional accuracy are low. The fact that the flow portion flows duringthe process ensures that any eccentricities etc. are compensated for byflown thermoplastic material.

Generally, the diameter of the distal portion (or shaft portion) of thefirst object will be approximately equal to or smaller than the diameterof the third object opening but will be larger than the diameter of theperforation so that when being pressed towards a distal directionrelative to the second object, the first object encounters a resistanceby the second object. When the first object is subject to the mechanicalvibration, this will lead to the liquefaction at the interface betweenthe second and first objects.

In embodiments of this group, the first object is provided having a headportion (or possibly a head portion is formed during the process). Thestep of coupling the mechanical vibration energy into the assembly,which step then includes pressing the first object towards a distaldirection relative to the second object (and also the third) object maythen be carried out until a distally facing shoulder formed by the headportion rests against the proximally facing surface of the third objectaround the mouth of the opening.

In a sub-group of embodiments of this group, the thermoplastic materialof the first object is chosen to have a glass transition temperaturethat is smaller than a temperature of the temperature reached during asubsequent electrodeposition process, which electrodepositiontemperature is for example 180° C. or 185° but to have a meltingtemperature substantially higher than this electrodepositiontemperature. Due to this, when the assembly is heated to theelectrodeposition temperature, the thermoplastic material is in arubber-like, flexible state that allows significant deformation (creep),and the material has a very high ductility to deform without failing, sothat different coefficients of thermal expansion may be compensated forby controlled temporal deformation of the thermoplastic material. If inembodiments the glass transition temperature is above room temperature,the thermoplastic material and as a consequence the connection willautomatically stiffen out again when the assembly is cooled back to thetemperature at which it is used. In embodiments, if the capability ofcompensating for thermal distortions is important, the thermoplasticmaterial of the first object may, at least at the attachment location,be chosen to be a thermoplastic elastomer.

In embodiments of this group, the first object may especially have abody of a not liquefiable material. Especially, such a body may form acore of the shaft portion. Optionally, if applicable, the body may alsoform the head portion. If the body forms the core of the shaft portion,the body shaft portion may optionally have an axial extension sufficientfor it to reach through the perforation. Then, the diameter of the bodyshaft portion may be approximately equal to the diameter of theperforation, or it may be smaller than this or it may be larger thanthis and will then cause a further deformation of the second objectaround the perforation when the first object is pressed against thesecond object.

In this text, the word “diameter” does not necessarily imply that theaccording structure (perforation, opening, shaft cross section, etc.)needs to be circular, although often circular shapes may be an option,especially because they are easy to manufacture. In case the accordingstructure is not circular, “diameter” denotes the average diameter,unless specified otherwise.

In embodiments, especially (but not only) of this group, if the firstobject has a body of a not liquefiable material, the body may beequipped to perforate the second object to cause the perforation. Forexample, a distal piercing tip or punching edge may be initially broughtinto contact with the second object, and a punching force is applied,optionally also mechanical vibration energy or other energy may becoupled into the first object. Thereafter, or already during thisperforation step, the thermoplastic material comes into contact with theedge generated by the perforation step and by the (simultaneous orsubsequent) energy input starts becoming flowable.

In embodiments of this group, the sheet portion around the perforationis deformed to project towards the distal side, i.e. to project awayfrom the side from which the first object is brought into contact withit and away from the third object. However, it would be possible toprovide the second object in a shape essentially flat around theperforation or even projecting towards the proximal side, into the thirdobject opening.

An even further group of embodiments also concerns securing a further,third object to the second object by the first object. In accordancewith this even further group, the third object like the second objecthas a generally flat sheet portion, with the sheet portion having anedge. As an option, the third object sheet portion may have a thirdobject perforation, with the edge running along the perforation.

For example, in embodiments of this even further group both, the secondand third objects may include metal sheets (or consist of metal sheets),of a same or of different material, the metal sheets forming therespective edges.

For the embodiments of this further group, the step of couplingmechanical vibration energy into the assembly includes couplingmechanical vibration energy into the assembly including the first,second and third objects until a flow portion of the thermoplasticmaterial due to friction heat generated between the edge and thethermoplastic material becomes flowable and flows around the edge to atleast partially embed the edge in the thermoplastic material and flowsaround the third object edge to embed the third object edge in thethermoplastic material, whereby after the step of stopping themechanical vibration the re-solidified thermoplastic material embedsboth, the (second object) edge and the third object edge to secure both,the second and third objects relative to the first object, whereby thesecond and third objects are secure to each other.

In this, the flow portion does not necessarily have to be contiguous.Rather, the flow portion may optionally have sub-portions that becomeflowable in contact with the second object edge and the third objectedge, respectively, with non-flowable portions of the first objectbetween them.

In embodiments of this further group, both, the second object edge andthe third object edge form a contour that is different from a simplestraight edge but that includes at least one bend or corner. This is forexample the case if the respective edge runs along a perforation. Forexample, both, the second and third objects each may have a perforation,with the respective edge along the perforation, and with the option ofthe perforations being, after the step of positioning, arrangedapproximately concentrically. With corresponding geometries, by thisalso connections that are secured against relative rotation orconnections at corners may be realized.

As an alternative to running along a perforation, the edges (or at leastone of the second and third object edges) may run along a peripheralpart of the respective object, with this peripheral part forming anaccording bent structure or structure having a corner, such as awave-like structure etc.

Due to being bent or having a corner, the shape of the edge gives theconnection additional stability, especially with respect to shear alongthe sheet plane.

In a first sub-group of embodiments of this further group, the secondand third objects in the step of positioning are brought into contactwith the first object from opposite sides, i.e., the first object issandwiched between the second and third objects. For example, the secondobject may be arranged so that the edge comes into contact with agenerally distally facing surface of the first object, and the thirdobject edge comes into contact with a generally proximally facingsurface of the first object. The second and third objects are thusanchored from opposed sides of the first object.

In this first sub-group, the mechanical vibration may be coupled intothe assembly via the third object or the second object, with the otherone of these objects and/or the first object resting against anon-vibrating support. Alternatively, the mechanical vibration energymay be coupled into both, the third object and the second object. Inaddition or as yet another alternative, the vibration may be coupleddirectly into the first object, with the second and third objects beingpressed against the first object from opposite sides.

In a second sub-group of embodiments, the second and third objects arebrought into contact with the first object from a same side. In this theedges of the second and third objects may be adjacent to each other andin embodiments run approximately parallel. For example, if the edges runalong respective perforations, the perforations of the second and thirdobjects may have different diameters and be arranged approximatelyconcentrically.

In embodiments of this second sub-group, the mechanical vibration may becoupled into the assembly by being coupled into the first object. It isalso possible to couple the vibration directly into the second and/orthird object. In the latter case, an intermediate element, for exampleof a polymer, may be put between the sonotrode and the respectiveobject, for example of silicone, PTFE, etc.

In embodiments, optionally but not necessarily of this group, in whichthe vibration energy is coupled into the assembly via the second object(and/or, if applicable, via the third object), the first object and thevibrating tool (sonotrode), by which the vibration is coupled into theassembly, may be adapted to each other so that in addition to a contactface between the tool and the second/third object, there is a contactface between the tool and the first object, wherein in the step ofcoupling the vibration energy into the assembly, thermoplastic materialof the first object is caused to become flowable at the interface to thetool and is caused to flow relative to the tool.

For example, the first object may include at least one protrusionprotruding from the respective face against which the edge of thesecond/third object is pressed. The protrusion may especially protrudefrom the plane defined by the edge beyond a sheet plane if the deformedsection along the edge is deformed to project towards the first object.This protrusion is by the effect of the vibration energy at least partlymade flowable and caused to flow, especially to fill gaps and to provideanother contribution to the securing.

In addition or as an alternative to the first object including aprotrusion, the sonotrode may include a protrusion so that the namedcontact face arises.

The present invention also concerns an arrangement for carrying out theinvention. The arrangement includes the first object having athermoplastic material in a solid state, the second object with agenerally flat sheet portion, with the sheet portion having an edge, thefirst object and second objects being capable of positioned relative toone another to provide an assembly including the first and secondobject, in which assembly the edge is in contact with the thermoplasticmaterial, the arrangement further optionally including a sonotrodecapable of coupling mechanical vibration energy into the assembly,and/or further optionally including a connector piece of the kinddescribed in this text. In addition or as an alternative, thearrangement may include a membrane interface between the sonotrode andthe respective object, for example as intermediate piece of the kindmentioned hereinbefore.

More in general, parts of the arrangement may have the propertiesdescribed referring to the different embodiments of the method taught inthis text. For example, the sheet portion may have a perforation alongwhich the edge runs.

The invention even further concerns a reinforcer portion or connectorpiece having the properties described in this text.

Moreover, the invention includes an object as described as furtherobject referring to the special sub-group mentioned hereinbefore, namelyan object including a plurality of connector portions, and for eachconnector portion a first object including a thermoplastic material, thefirst objects shaped to be releasably/reversibly fastened to therespective connector portion.

Generally, the first and second and, if applicable, third objects areconstruction components (construction elements) in a broad sense of theword, i.e. elements that are used in any field of mechanical engineeringand construction, for example automotive engineering, aircraftconstruction, shipbuilding, building construction, machine construction,toy construction etc. Generally, the first and second objects as well asa connector piece (if applicable) will all be artificial, man-madeobjects. The use of natural material such as wood-based material in thefirst and/or second object is thereby not excluded.

The second object may be any object that has a flattish sheet portion.“Sheet portion” in this does not imply a necessarily homogeneousthickness. The second object may especially be a metal sheet.Alternatively, the second object may be another object having a sheetportion, for example a more complex object having a part of a metalsheet, which part constitutes the sheet portion, or an object in which asheet portion is constituted not by a metal sheet in the narrow sense ofthe word (manufactured by rolling) but by a for example metallic partmanufactured in a cast process, such as a die cast object.

Turning back to the thermoplastic material of the first object, in thistext the expression “thermoplastic material being capable of being madeflowable e.g. by mechanical vibration” or in short “liquefiablethermoplastic material” or “liquefiable material” or “thermoplastic” isused for describing a material including at least one thermoplasticcomponent, which material becomes liquid (flowable) when heated, inparticular when heated through friction i.e. when arranged at one of apair of surfaces (contact faces) being in contact with each other andvibrationally moved relative to each other, wherein the frequency of thevibration has the properties discussed hereinbefore. In some situations,for example if the first object itself has to carry substantial loads,it may be advantageous if the material has an elasticity coefficient ofmore than 0.5 GPa. In other embodiments, the elasticity coefficient maybe below this value, as the vibration conducting properties of the firstobject thermoplastic material do not play a role in the process. Inspecial embodiments, the thermoplastic material therefore may eveninclude a thermoplastic elastomer.

Thermoplastic materials are well-known in the automotive and aviationindustry. For the purpose of the method according to the presentinvention, especially thermoplastic materials known for applications inthese industries may be used.

A thermoplastic material suitable for the method according to theinvention is solid at room temperature (or at a temperature at which themethod is carried out). It preferably includes a polymeric phase(especially C, P, S or Si chain based) that transforms from solid intoliquid or flowable above a critical temperature range, for example bymelting, and re-transforms into a solid material when again cooled belowthe critical temperature range, for example by crystallization, wherebythe viscosity of the solid phase is several orders of magnitude (atleast three orders of magnitude) higher than of the liquid phase. Thethermoplastic material will generally include a polymeric component thatis not cross-linked covalently or cross-linked in a manner that thecross-linking bonds open reversibly upon heating to or above a meltingtemperature range. The polymer material may further include a filler,e.g. fibres or particles of material which has no thermoplasticproperties or has thermoplastic properties including a meltingtemperature range which is considerably higher than the meltingtemperature range of the basic polymer.

In this text, generally a “non-liquefiable” or “not liquefiable”material is a material that does not liquefy at temperatures reachedduring the process, thus especially at temperatures at which thethermoplastic material is liquefied. This does not exclude thepossibility that the material would be capable of liquefying attemperatures that are not reached during the process, generally far (forexample by at least 80° C.) above a liquefaction temperature (meltingtemperature for crystalline polymers for amorphous thermoplastics atemperature above the glass transition temperature at which the becomessufficiently flowable, sometimes referred to as the ‘flow temperature’(sometimes defined as the lowest temperature at which extrusion ispossible), for example the temperature at which the viscosity drops tobelow 10⁴ Pa*s (in embodiments, especially with polymers substantiallywithout fiber reinforcement, to below 10³ Pa*s)), of the thermoplasticmaterial. For example, the non-liquefiable material may be a metal, suchas aluminum or steel, or wood, or a hard plastic, for example areinforced or not reinforced thermosetting polymer or a reinforced ornot reinforced thermoplastic with a melting temperature (and/or glasstransition temperature) considerably higher than the meltingtemperature/glass transition temperature of the liquefiable part, forexample with a melting temperature and/or glass transition temperaturehigher by at least 50° C. or 80° C. or 100° C.

In this text, “melting temperature” is sometimes used to refer to thenamed liquefaction temperature at which the thermoplastic materialbecomes sufficiently flowable, i.e. the conventionally defined meltingtemperature for crystalline polymers and the temperature above the glasstransition temperature at which the thermoplastic material becomesflowable sufficiently for extrusion.

Specific embodiments of thermoplastic materials are: Polyetherketone(PEEK), polyesters, such as polybutylene terephthalate (PBT) orPolyethylenterephthalat (PET), Polyetherimide, a polyamide, for examplePolyamide 12, Polyamide 11, Polyamide 6, or Polyamide 66,Polymethylmethacrylate (PMMA), Polyoxymethylene, orpolycarbonateurethane, a polycarbonate or a polyester carbonate, or alsoan acrylonitrile butadiene styrene (ABS), anAcrylester-Styrol-Acrylnitril (ASA), Styrene-acrylonitrile, polyvinylchloride, polyethylene, polypropylene, and polystyrene, or copolymers ormixtures of these.

In addition to the thermoplastic polymer, the thermoplastic material mayalso include a suitable filler, for example reinforcing fibers, such asglass and/or carbon fibers. The fibers may be short fibers. Long fibersor continuous fibers may be used especially for portions of the firstand/or of the second object that are not liquefied during the process.

The fiber material (if any) may be any material known for fiberreinforcement, especially carbon, glass, Kevlar, ceramic, e.g. mullite,silicon carbide or silicon nitride, high-strength polyethylene(Dyneema), etc.

Other fillers, not having the shapes of fibers, are also possible, forexample powder particles.

Mechanical vibration or oscillation suitable for embodiments of themethod according to the invention has preferably a frequency between 2and 200 kHz (even more preferably between 10 and 100 kHz, or between 20and 40 kHz) and a vibration energy of 0.2 to 20 W per square millimeterof active surface.

In many embodiments, especially embodiments that include coupling thevibration into the first object, the vibrating tool (e.g. sonotrode) ise.g. designed such that its contact face oscillates predominantly in thedirection of the tool axis (the proximodistal axis, corresponding to theaxis along which the first object and second objects are moved relativeto one another by the effect of the energy input and pressing force whenthe edge is caused to penetrate into material of the first object;longitudinal vibration) and with an amplitude of between 1 and 100 μm,preferably around 30 to 60 μm. Such preferred vibration is e.g. producedby ultrasonic devices as e.g. known from ultrasonic welding.

In other embodiments, the vibration is transverse vibration, i.e.oscillation predominantly at an angle, for example perpendicular, to theproximodistal axis and hence for example parallel to a contact facebetween the first and second objects. Vibration energy and amplitude inthis may be similar to the above-mentioned parameters of longitudinalvibration.

In a further group of embodiments, which may be viewed as a sub-group ofembodiments with transverse vibration, the oscillation may be rotationaloscillation, i.e. the vibrating item vibrates in a back and forthtwisting movement. For rotational oscillation to be an option, thesecond object should not have a rotation preventing geometry in that forexample the edge extends circularly around a perforation. Also, thiskind of oscillation is especially suited for set-ups in which the firstobject is comparably small, especially if it is a connector or belongsto a connector.

Depending on the application, a vibration power (more specifically: theelectrical power by which an ultrasonic transducer is powered) may be atleast 100 W, at least 200 W, at least 300 W, at least 500 W, at least1000 W or at least 2000 W.

In this text, the terms “proximal” and “distal” are used to refer todirections and locations, namely “proximal” is the side from which anoperator or machine applies the mechanical vibration, whereas distal isthe opposite side.

The side of the first object that is brought into contact with thesecond object in this text is sometimes called “contact side”. Inembodiments, in which the first object is positioned proximally of thesecond object and the vibration is applied to the first object that ispressed against the second object, the contact side is the distal sideand includes the distally facing face into which the edge of the secondobject is pressed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, ways to carry out the invention and embodiments aredescribed referring to drawings. The drawings are all schematical. Inthe drawings, same reference numerals refer to same or analogouselements. The drawings show:

FIGS. 1a and 1b an embodiment of a second object with a securinglocation;

FIGS. 2a and 2b an alternative embodiment of a second object;

FIGS. 3a-5b in cross section, different configurations in an initialstage of the method and after the method has been carried out;

FIGS. 6-8 different embodiments of connector pieces;

FIGS. 9 and 10 are further alternative configurations;

FIGS. 11-13 alternative sonotrode designs;

FIGS. 14a-14c an embodiment of the reversible fastening of a furtherobject to the second object by means of the first object;

FIGS. 15-16 yet other configurations for carrying out the invention;

FIGS. 17a and 17b yet another second object with a securing locationincluding a plurality of perforations;

FIGS. 18a and 18b a configuration in which a third object is secured tothe second object by the first object in an initial and a final stage,respectively;

FIGS. 19-22 different first objects for a configuration substantially asshown in FIGS. 18a and 18 b;

FIGS. 23 and 24 variants of this configuration;

FIGS. 25a and 25b a further configuration in which a third object issecured to the second object by the first object in an initial and afinal stage, respectively;

FIG. 26 a variant of the configuration of FIG. 25 a;

FIGS. 27-29 variations of properties of the sheet portions along theedge;

FIG. 30 an even further configuration in which a third object is securedto the second object by the first object at an initial stage;

FIG. 31 a further configuration of a first object and a second object;

FIG. 31a a variant of the first object for a configuration as the one ofFIG. 31;

FIGS. 32 and 33 yet further configurations for securing a third objectto the second object by the first object;

FIGS. 34a and 34b different edge structures;

FIGS. 35a and 35b a further variant of a configuration;

FIGS. 36 and 37 further alternative configurations;

FIG. 38 a process diagram;

FIG. 39 a configuration with an elastomeric sealing element;

FIG. 40 a process diagram for the configuration of FIG. 39;

FIG. 41 a further configuration with an elastomeric sealing element;

FIGS. 42 and 43 even further configurations for securing a third object,the second object and the first object to each other;

FIG. 44 the principle of a second object with a plurality of attachmentlocations;

FIGS. 45a and 45b a second object with a plurality of attachmentlocations in which the attachment locations together lock the firstobject relative to the second object in all in-plane directions;

FIG. 46 the principle of tolerance compensation;

FIG. 47 a dependence of the minimal depth on the angle;

FIG. 48 a configuration with a second object having a sheet plane notperpendicular to the axial direction and also illustrating the principleof angle mismatch compensation;

FIG. 49 a first object with a functional zone and attachment zones;

FIGS. 50a and 50b a configuration for guiding the first object duringthe process;

FIG. 51 attaching a holder by the approach according to the invention;

FIG. 52 a snap connector attached by the approach according to theinvention;

FIG. 53 a vibration decoupling;

FIG. 54 an embodiment with a die cast second object;

FIGS. 55-56 configurations with an anchoring part and an adjustmentpart;

FIGS. 57a and 57b an anchoring part and an adjustment part of an otherembodiment;

FIGS. 58a-58c yet another embodiment of an anchoring part and anadjustment part and details thereof;

FIGS. 59-60 further configurations of a first object, and adjustmentpart, and a second object, wherein the first object serves as anchoringpart;

FIGS. 61a and 61b a configuration of a second object and a first objectduring different stages of adjusting;

FIGS. 62-63 configurations in which a connector piece serves asadjustment part;

FIGS. 64a and 64b a configuration in which the connector piece has atapered portion cooperating with a tapered opening during differentstages;

FIG. 65 another configuration in which a connector piece serves asadjustment part;

FIGS. 66-68 inserts that may serve as connector pieces or as parts of anadjustment part that also includes liquefiable material;

FIGS. 69 and 70 attachment flanges with an elastic joint;

FIG. 71 an attachment flange with a dedicated coupling surface portion;

FIG. 72 a first object with different thermoplastic material parts;

FIG. 73-76 configurations implementing the principle of providing thecontact side with structures;

FIGS. 77-79 different cross sections of protrusions of first objectsthat implement the principle illustrated in FIGS. 73-76;

FIGS. 80 and 81 a configuration with the second object having a mainperforation and a plurality of peripheral perforations;

FIGS. 82-84 configurations with a second object having an asymmetricaldeformed section;

FIGS. 85 and 86 the principle of z position control by the first objecthaving a spacer;

FIGS. 87-91 configurations implementing the principle of restricting thecoupling face between a sonotrode and the first object to a regiontailored to the shape and location of the second object;

FIGS. 92 and 93 two basic configurations for adjusting an in-planeposition;

FIGS. 94 and 95 embodiments of the basic configuration of FIG. 92;

FIGS. 96-102 embodiments and principles of the basic configuration ofFIG. 93;

FIG. 103 a fastener as an example of a second object;

FIGS. 104-106 principles of coupling mechanical vibration into thesecond object;

FIG. 107 a two station manufacturing line;

FIGS. 108-110 sonotrode designs and configurations for couplingtransverse vibration into a second object; and

FIGS. 111-113 configurations, in which the second object has anextension opening;

FIGS. 114 and 115 a first configuration with an anvil;

FIGS. 116-118 further configurations with an anvil;

FIGS. 119 and 120 a configuration with a first object having anattachment structure; and

FIG. 121 a flowchart of a method that includes adjusting a position.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1a and 1b show, in a top view and in cross section, an example ofa metal sheet 2 being a second object. The metal sheet includes aperforation 20, for example made by a punching tool. For example, theperforation may be made by slowly pressing a tool with a tip against themetal sheet while the same is placed against a support with an openingat the place where the tool acts, until the tip of the tool comesthrough. The shape of the perforation will be irregular, with aplurality of tongues. Alternatively, the shape could be regular if acorresponding geometry had been punched or cut (by a water jet or laser)before or been shaped in a prior sheet forming process. Around theperforation 20, the metal sheet forms an edge 21 that in the subsequentsteps has the function of an energy director. The parameters height h,(average) diameter d of the perforation, diameter D of the d sectionthat is deformed to project away from the metal sheet plane and—in somesituations better defined than the diameter d of the perforation—theangle α, here defined as the angle between the deformed section and thevertical to the metal sheet plane—are depicted in FIG. 1 b; theaccording definition is used throughout this text.

As an alternative to being perforated irregularly, by means of asuitable punching device in combination with pre-cutting the centralhole geometry (e.g. by laser) one can also manufacture an irregular orregular, for example circular perforation as shown in FIGS. 2a and 2 b.

With reference to FIGS. 3a and 3b basic principles of many embodimentsas well as a particular embodiment of the method according to theinvention are described.

The first object 1 includes thermoplastic material. In the depictedembodiment, the first object is illustrated to have a panel shapedsection that consists of the thermoplastic material and defines aproximally facing face 11—serving as the mentioned coupling face—and adistally facing face 12 that when the first object is positionedrelative to the second object 2 is brought into contact with theprojecting section around the perforation 20. However, more generally,the first object 1 may have other shapes, and may have an inhomogeneousmaterial composition. A few examples are shown in embodiments describedhereinafter.

More in general, the first object may be the part to be connected, or aportion thereof, or a connecting element (dowel, base of a clip, rivet,etc.).

-   -   If the first object is the part to be connected—that includes a        portion of the thermoplastic material as many parts in        mechanical engineering and construction do—itself, then the        approach of the invention in addition to the general advantages        of the invention (low cost assembly and parts, sound anchoring,        sealingly tight connection possible) also features the        advantages:        -   that in contrast to the fastening of the by fasteners            cooperating with well-defined fastening structures, the            position with respect to the first object needs to be            defined with generally much less precision, thus with            substantially increased tolerances, and        -   that fewer parts and fewer assembly steps are required.    -   If the first object is a separate connecting element, in        addition to the general advantages the approach according to the        invention brings about a substantial flexibility with respect to        the choice of shape and properties of the connecting element as        well as, for example together with the approach described        referring to FIGS. 14a-14c hereinafter, also the advantage of        the less tight tolerances than prior art methods.

For securing the first object to the second object, a vibratingsonotrode 6 presses the first object against the second object in avicinity of the perforation 20. Mechanical vibration energy therebycoupled into the first object propagates via the first object 1 and isabsorbed at the places where the first object is in contact with theedge 21 that thereby serves as an energy director. As a consequence, thethermoplastic material around the edge is heated and becomes flowable,allowing the projecting section of the sheet material to be pressed intothe body of the first object. After re-solidification, this leads to ananchoring at least of the projecting section in the first object andthereby to a mechanical positive-fit connection between the first andsecond objects. The resulting arrangement is shown in FIG. 3b . ThisFigure schematically illustrates material portions 14 that have flown tounderneath the second object and thereby cause the mentioned anchoring.

In a group of embodiments, the material flow underneath the secondobject is assisted and/or directed by an appropriately shaped anvilstructure. The principle of this—that may be used in any embodiment ofthe invention that allows access of the securing location from thedistal side, i.e. the side opposite to the side from which the sonotrodeimpinges, including embodiments described referring to other figures notin the present text, which other figures do not explicitly show suchanvil structure—is schematically illustrated in FIG. 114. An anvil 600is used to support the second object during the securing process. Theanvil 600 is different from being just flat but includes a directingprotrusion 601 and a receiving depression 602 around it. As shown inFIG. 115 by arrows, the directing protrusion 601 assists to consolidatethe thermoplastic material distally of the second object and therebyenhances the overall stability and reduces the required penetrationdepth.

In the embodiment of FIGS. 4a and 4b , the first object 1 is not panelshaped but rather is stud-like. In addition to the portion 15 of thethermoplastic material it has a reinforcer portion 16 of a material thatis not liquefiable under the conditions that apply during the process.Especially, the reinforcer portion may be metallic. In the depictedembodiment, the reinforcer portion 16 is a bushing, optionally with athread or other structure that allows securing a further element to it.As can especially seen in FIG. 4b , such a reinforcer portion 16 in may,in addition to an other function it may have (such as, as mentioned, besuitable for securing a further element to it) may also bring aboutadditional mechanical stability to the connection between the first andsecond objects. For example, as in the depicted configuration, it mayextend into the perforation and thereby stabilize the connection betweenthe first and second objects with respect to possible shearing forcesacting on it.

A further function of the reinforcer portion 16 is that it assists thecontrol of the flow of the thermoplastic material by forcing thethermoplastic material to flow towards distally and sideways. Therebythe reinforcer portion 16 has a similar function as the anvil describedreferring to FIG. 114, with the difference that the location does notneed to be accessible from distally.

In some embodiments like the one of FIG. 4a /4 b it may be advantageousto ensure that the mechanical vibration is not coupled directly into thereinforcer portion to prevent any situation in which the thermoplasticmaterial around the reinforcer portion is liquefied and the position ofthe reinforcer portion thereby is de-stabilized. To this end, the firstobject and the sonotrode may be shaped so that the coupling face isrestricted to areas around the reinforcer portion, as describedhereinafter for example referring to FIGS. 87-91.

In a group of embodiments, the method includes the further step ofproviding a further connector piece 3 that is initially separate fromthe first and second objects and that in the method of securing isassembled together with the first and second objects to yield amonolithic assembly. FIG. 5a illustrates an example of such a connectorpiece 3. The connector piece in the depicted embodiment has a distal tipand retaining structures 31 along a lateral periphery. Prior to the stepof coupling the mechanical vibration energy into the first object, thesonotrode 6 is used to couple energy and a pressing force into theconnector piece thereby driving the connector piece into the firstobject 1, wherein material of the first object is locally liquefied byabsorbed mechanical energy where the connector piece 3 is in contactwith it. Once the proximal end face of the connector piece 3 is flushwith the proximally facing face 11 of the first object 1, the processcontinues as described referring to FIGS. 3a and 3b . By suitablesonotrode designs (see for example FIGS. 11 and 12 describedhereinafter), the depth by which the connector piece is driven into theassembly of the first and second object may be set. The retainingstructures in the assembled state will be interpenetrated by liquefiedand re-solidified thermoplastic material, whereby they bring additionalmechanical stability. FIG. 5b depicts the assembly after the process.

A connector piece 3 may have a similar function as a reinforcer portionof the hereinbefore mentioned kind, and teachings in this text referringto properties of the reinforcer portion may be applicable also forconnector pieces, and vice versa, the main difference being that thereinforcer portion is initially, prior to the coupling of energy intothe arrangement, a part of the first object, in contrast to theconnector piece.

FIGS. 6, 7, and 8 yet show variants of connector pieces 3 (or ofreinforcer portions). The connector piece 3 of FIG. 6 has an attachmentpeg 32 onto which a further element may be clipped. Optionally, afterthe securing process, it may have a similar function as the fasteningclips described referring to FIGS. 14a-14c hereinafter, the differencebeing that the portion to which the further element is clipped is aportion of the connector piece 3 (or reinforcer portion) and not of thethermoplastic portion.

For the process with the connector piece 3 of FIG. 3, it may beadvantageous to use a ring sonotrode (tubular sonotrode; see FIG. 13hereinafter) so that the attachment peg 32 is not in direct contact withthe sonotrode.

As a further difference to the embodiment of FIG. 5a , which differenceis independent of the attachment peg, the distal end does not have a tipbut a distally facing edge 33 that has a similar function as the tip butwill have an influence on the material flow control by increasing thetendency of the thermoplastic material to flow into distaldirections—depending on the assembly situation, this may be desired ornot.

The connector piece 3 embodiment of FIG. 7 is a bushing with an innerthread 39 and outer retaining structures 31.

In the embodiment of FIG. 8, the connector piece in addition to a distaltip 36 and to retaining structures 31—and independently of these—has ahead portion 34 with a proximally facing flange portion 35 thatcontributes to the flow control of thermoplastic material. Especially,it prevents thermoplastic material of the first object 1 from flowingsideways at more proximal positions, thereby forcing it to flow wherethe second object 2 is arranged, thus contributing to a more pronouncedmechanical securing.

Referring to FIG. 9, a similar principle is shown but with a flangeportion 18 constituted by thermoplastic material of the firstobject—also this will at least initially cause a flow control to preventa sideways flow. Combinations, for example with a not thermoplasticflange portion attached to thermoplastic material of the first object,are possible.

In the variant of FIG. 10, the first object 1 has a reinforcer portion16, which, however, protrudes on the proximal side above the proximalend face of the thermoplastic portion 15, whereby the first object isdesigned for the reinforcer portion 16 to be moved relative to thethermoplastic portion 15 during the process, whereby thermoplasticmaterial of the thermoplastic portion 15 is displaced.

The embodiment of FIG. 10 may especially be advantageous if thereinforce itself is of a plastically deformable material. Then, thedistal portions of the reinforcer portion 16, such as distal feetportions as shown in FIG. 16, are, by the pressure caused by thethermoplastic material distally of it, deformed outwardly and therebycontribute to the anchoring strength. In this, the reinforcer portionitself may be of a thermoplastic material that is such that themechanical vibration and the pressing force are capable of beingtransmitted through the reinforcer portion at least in part while thereinforcer portion 16 is nevertheless deformable. For example, to thisend the reinforcer portion may be of a thermoplastic material with ahigher liquefaction temperature than the material of the thermoplasticportion 15, or of a material based on the same polymer but with a higherfilling grade so that its viscosity is higher. Alternatively, it may beof a bendable metal in which case the portions that are to be deformedare accordingly sufficiently thin.

This process of deforming a reinforcer portion 106 may especially beassisted by an anvil (not shown in FIG. 10), for example with a centraldirecting protrusion 601, as for example illustrated in FIG. 114.

FIGS. 11, 12, and 13 show alternative sonotrode designs. The sonotrode 6of FIG. 11 has a distal peripheral flange 61 that may, depending on theset-up, either confine the lateral flow of thermoplastic material orpress the reinforcer portion/connector piece to a into a different depththan the material around it or both. The distal protrusion 62 of thesonotrode 6 of FIG. 12 may have a guiding function, for example togetherwith a guiding indentation of the first object or the connector piece,and/or may have the function of driving the connector piece orreinforcer portion further into the assembly of the first and secondobjects. The sonotrode 6 of FIG. 13 is a ring sonotrode. In mostembodiments, the ring sonotrode will be designed such that the distaloutcoupling end face of the sonotrode covers lateral positions of theprojecting section of the second object 2.

With respect to FIGS. 14a-14c a particular configuration suitable forembodiments of the invention is described. The configuration relates toreversibly fastening a further object to the second object at aplurality of fastening locations. FIG. 14a shows a flattish plateelement 71 as an example of such a further object to be removablyfastened to a surface of an object with a flat surface (the secondobject). An application of this configuration for example includes thefastening of number plates to a car body.

In accordance with embodiments of the invention, in contrast, the fixingconnectors are provided as first objects 1 (or as connector pieces ofthe above-defined kind) in a method as described herein. To this end,the first objects 1 (as illustrated in FIG. 14a ) or the connectorpieces (for example as shown in FIG. 6) are provided with a clippingconnection structure 13, illustrated to be a peripheral groove in FIG.14a , which clipping connection structure cooperates with an accordingstructure of the further element (the plate element 71 in FIG. 14a ) toyield a releasable clip-on connection. For securing the fixingconnectors to the second object 2, the first objects 1 are brought intocontact with correspondingly positioned projecting sections of thesecond object 2 while they are fastened to the further element (theplate element 71 in the depicted embodiment). Thereafter, the process iscarried out as described hereinbefore. As illustrated by the doublearrow 73 in FIG. 14b , the relative positioning of the first object andof the protruding sections in this need not be very precise and can,without adversely affecting the securing, vary within tolerances thatare given by the dimensions of the first object relative to thedimensions of the projecting sections. Thus, the tolerances for thepositioning of the attachment points (the perforations and deformedsections) with respect to the positions of the attachments structures(connector portions) of the further element 71 are much more relaxedthan for prior art methods. Nevertheless, the positions of thereleasable clip-on connection are fixed precisely due to the fact thatthe first objects 1 (or the connector pieces) are attached to thefurther element during the securing process. FIG. 14c shows theresulting assembly with the further element (the plate element 71) beingreleasably clipped to the second object 2.

FIG. 15 yet shows an embodiment in which the second object does not havea section that projects into the proximal direction, i.e. towards thefirst object. Rather, the perforation 20 is punched out (or drilled orotherwise removed), with its rim being in the sheet plane. In contrastto the previously described embodiments, method then does not work for asimply plate-shaped first object. Rather, the shape and position of thefirst object needs to be adapted. More in concrete, in the depictedembodiment the first object 1 is an attachment bolt with a taperingsection 101 and a head section 102, wherein the tapering section isdimensioned so that upon insertion into the perforation and movement todistal directions it encounters a substantial and rising difference bythe second object. When the sonotrode 6 presses the first object intothe perforation while energy is coupled into it, this will similarly tothe above-described embodiments cause the liquefaction of thermoplasticmaterial of the first object.

Simultaneously, the connector piece 3 (or alternatively a reinforcerportion) driven into the thermoplastic material will generate anoutwardly directed pressure on the flowable material. As a result, therim of the perforation becomes embedded in the thermoplastic material.The process may be carried out until the distally facing face of thehead section 102 abuts against the sheet material of the second object.Due to the used effect of the connector piece 3 (or reinforcer portion)driven into thermoplastic material of the first object 1, the shape ofthe inserted section 101 does not necessarily need to be tapering.

Instead of having a tapering section, the first object may have othershapes, including stepped or cylindrical with a diameter slightly largerthan the diameter of the perforation.

Embodiments that include driving a connector piece or reinforcer portioninto the thermoplastic material to generate an outwardly directedpressure, the connector piece/reinforcer portion has an effect similarto the effect of a structured anvil as mentioned hereinbefore. However,such embodiments feature the advantage that they are applicable also insituations in which the fastening location is not accessible from thedistal side.

In the variant of FIG. 16, the metal sheet that constitutes the secondobject around the perforation has a section that projects away from thefirst object. Especially, the second object may be formed as shown inFIGS. 1a and 1 b, but upside-down, so that it has a plurality of tonguesbetween which the thermoplastic material may flow. Also in thisembodiment, the dimensions of the perforation/deformed section on theone hand and of a projecting portion of the first object are adapted toeach other in a manner that there is substantial resistance against aforward (distal movement) of the first object with respect to the secondobject when the projecting portion of the first object is inserted inthe perforation. Also this embodiment may be combined with a connectorpiece or a reinforcer portion of the kind discussed in this texthereinbefore.

FIGS. 17a and 17b yet show an example of a second object in which aplurality of perforations 20 are arranged within a common deformedsection projecting away from the proximal side. A single first object 1of the kind illustrated in FIGS. 15 and 16 may be anchored in the dintformed by this deformed section, by the process as describedhereinbefore.

Applications include fastening a plastic part to a metal part (whereinthe second object is the metal part or a portion thereof) for example inthe automotive industry or the aviation industry. For example, in theautomotive industry, lightweight parts of plastic or composites oftenhave to be attached to the car body.

Whereas all described embodiments rely on the coupling of the mechanicalenergy into the assembly generally from the side of the first object(from the top in the figures), embodiments in which the mechanicalvibration energy is coupled into the second object are also possible.For example, in a configuration such as the one of FIG. 3a , thesonotrode 6 could act from the side that is shown as the lower side inthe figure.

FIGS. 18a -24 show embodiments of the group that includes securing athird object to the second object by the first object, especially insituations with accessibility only from one side, i.e. the proximal side(depicted as the top side in the Figures). In all these embodiments, thethird object 8 is illustrated as a flat CFK part. However, theembodiments of this group also work for third objects being for examplemetallic or of ceramic material or of a plastic (that is for example notliquefiable in the sense that it does not liquefy at the temperaturereached during the process) or any other suitable material used inconstruction. Also, the second object is depicted as metal sheet.However, the method works also for other materials capable of forming anedge around a perforation. The method is especially advantageous forconfigurations in which the second and third objects have differentcoefficients of thermal expansion; however, this is not a requirementfor the method to be useful.

The first object 1 in FIG. 18a serves as a connector for securing thethird object 8 to the second object 2. The first object has a portion 15of the thermoplastic material as well as a reinforcer portion 16 being anon-liquefiable core portion, for example of a metal. The core portion16 forms a head portion 91 of the first object and runs in an interiorof a shaft portion. In the depicted configuration, the core portion 91is coated by the thermoplastic material portion 15 along the entireshaft, however, it would be possible to provide the thermoplasticmaterial portion only as partial coating, for example leaving the distalend of the core portion free of any coating or leaving certain sectionsaround the periphery free of any coating.

The third object has a third object opening 81 being a through opening.The second object 2 has a shape substantially similar to the shape shownin FIG. 16. The diameter (compare FIG. 1b ) of the perforation issmaller than the diameter of the third object opening. More inparticular, the cross section of the shaft portion 92 is such that itfits through the opening but does not fit through the perforation.

After the first object has been inserted through the opening and pressedagainst the distal direction, against the second object 2 by a sonotrode6 by which at the same time mechanical vibration energy is coupled intothe first object 1, thermoplastic material becomes flowable. The processis continued until the head portion 91 causes the advance movement(movement into the distal direction) of the first object to stop. Then,the vibration energy input is stopped and the sonotrode removed. FIG.18b shows the result with the material portions 14 having flown todistally of the second object forming a blind rivet-like foot portion.Thus, in the configuration of FIG. 18b , first object after the processforms a rivet, with the second and third objects being clamped betweenthis foot portion and the head portion 91. If the glass transitiontemperature of the thermoplastic material used is somewhere between roomtemperature and about 160° C., the rivet connection has thehereinbefore-discussed advantages in terms of compensating for differentcoefficients of thermal expansion in an electrodeposition process, forexample of a painting/lacquer. As an example, acrylonitrile has a glasstransition temperature of about 130° C.-140° C.

FIG. 19 shows a variant of a first object in which the core portion 16has a distal punching edge 93. Such distal punching edge may in theprocess be used to punch out the perforation.

As a further variant, FIG. 20 shows a first object with the (metallic)core portion forming a distal piercing tip 94. Such piercing tip may beused to cause the perforation including the deformation around the mouth(as shown in FIG. 18a ) by piercing the metal sheet that forms thesecond object.

In embodiments that include piercing, optionally a waisted portion 96may be present so that after the piercing step the sheet portion doesnot clamp the core portion any more, and relative vibration becomespossible.

In both embodiments, the one of FIG. 19 and the one of FIG. 20, theprocess may be continued after the punching/piercing step substantiallyas described referring to FIGS. 18a and 18 b.

FIG. 21 shows, as an even further variant, a first object suitable forthe group of embodiments that includes securing a third object to thesecond object by the first object, which object does not have a coreportion or other reinforcer portion but which consists of thethermoplastic material. Also in this embodiment, a head portion 91 maybe present as an option, in addition to the shaft portion 92.

The embodiment of FIG. 22 shows further feature that may be realized incombination or on their own, or independently of each other.

-   -   The core portion 16 includes structures 95 suitable of making a        positive-fit connection (here: with respect to relative        movements in axial directions) or otherwise enhancing the        connection between the core portion 16 and the thermoplastic        material portion 15.    -   The core portion has a smaller axial extension (extension along        the proximodistal axis) so that it does not necessarily reach        through the perforation. More in general, there is no        requirement of a particular extension/dimension of the core        portion (if any), although in configurations in which        substantial shear forces are to be expected between the second        and third objects, it may be advantageous if such core portion        reaches both, through the opening and the perforation.

In the variant of FIG. 23, the second object 2 around the perforation isnot bent to project away from the third object (in contrast to what isshown in FIG. 18a ) but is essentially flat.

While an anvil may be beneficial in many embodiments of the invention,including embodiments the description of which does not mention theanvil in an embodiment like the one of FIG. 23 an anvil with acorresponding surface structure, as described hereinbefore, may beespecially beneficial to direct a material flow to distally of theportions of the second object along the edge 21.

In the variant of FIG. 24, the second object has a shape substantiallyas described referring to FIGS. 17a and 17b , with a plurality ofsmaller protrusions instead of one bigger protrusion.

FIG. 25a shows an example of an arrangement for securing a third object4 to a second object 2 by means of a first object 1, wherein both, thesecond and third object have a generally flat sheet portion, with thesheet portion having an edge.

In the embodiment of FIG. 25a , the second object has a second objectperforation 20 along which the second object edge 21 runs, and the thirdobject 4 has a third object perforation 40 along which the third objectedge 41 runs. Along the perforation, the respective objects 2, 4 aredeformed so that the sheet material projects away from the respectivesheet plane.

The objects 1, 2, 4 are arranged so that the first object is sandwichedbetween the second and third objects and that the sheet material of thesecond and third objects projects towards the first object 1, i.e.projects towards the proximal side for the second object 2 and projectstowards the distal side for the third object 4.

During the process, opposite pressing forces are applied to the secondand third objects, whereby the first object is clamped between thesecond and third objects. At the same time, mechanical vibration energyis coupled into the assembly. To this end, for example a vibratingsonotrode 6 presses the third object 4 against the first object 1,whereby the first object 1 is pressed against the edge 21 of the secondobject, which in turn is placed against a non-vibrating support 7 thatapplies the opposite pressing force as the normal force.

In the embodiment of FIG. 25a , the vibration is coupled into thearrangement via the third object. At the onset of the vibration, beforematerial portions become flowable, the vibration of the third objectcauses the first object to vibrate also. If the parameters (angle α,acuteness of the edge, length of the edge, stiffness of the materials,etc.) of the objects are chosen appropriately the heating process at theinterface to the second object edge 21 sets in before it starts at theinterface to the third object edge 41, or approximately simultaneously.Especially, the second object edge 21 may be formed to have a strongertendency to absorb energy at the interface (for example by beingsteeper) than the third object edge 41. Thereby, anchoring of both, thesecond and third objects in the first object may be achieved even if thevibration is coupled only into the third object.

FIG. 25b schematically shows the situation after the energy input hasstopped, with the flow portion 14 having sub-portions having flown alongthe edges of the second and third objects.

In accordance with the variant shown in FIG. 26, both, the second object2 and the third object 4 are subject to mechanical vibration, whereinthe assembly of the second object 2, the first object 1, and the thirdobject 4 is clamped between two vibrating sonotrodes 6.1, 6.2 applyingopposite pressing forces. This embodiment is less sensitive to theproperties of the edges of the second and third objects.

FIGS. 27-29 illustrate how properties of the edge may be varied toinfluence the energy absorption, for example for asymmetrical set-upswith energy input only from one side, as discussed referring to FIG. 25a. Parameters that may be varied include the steepness (angle α, FIG.27), the length of the edge (FIG. 28), the acuteness of the edge (FIG.29) and others.

FIG. 30 depicts another example of an embodiment the second and thirdobjects in which the second and third objects are brought into contactwith the first object from opposite sides. In contrast to theembodiments of FIGS. 25a and 26, however, the first object includes atleast one protrusion—two ridges 117, 118 in the depicted embodiment—,that projects from the respective proximally/distally facing face 11, 12against which the edge 21, 41 of the second/third object is pressed. Theridges 117, 118 (or other protrusion(s)) are designed so that theirheight is larger than or equal to or only a bit smaller than the heighth (see FIG. 1b ) of the respective deformed section along the edge. Whenthe sonotrodes 6.1, 6.2 are pressed against the third and second objects4, 2, they therefore come into direct contact with the sonotrode so thatduring the process mechanical vibration energy impinges on their endportions 113, 114, whereby the material at these end portions becomesflowable and may fill spaces along the edge, as illustrated by thearrows in FIG. 30. In addition or as an alternative to protrusions ofthe illustrated height, the respective sonotrode 6.1, 6.2 could beprovided with a protrusion.

The flowable material that has been generated at the interface betweenthe protrusion and the sonotrode may contribute to securing thesecond/third object to the first object, for example by contributing toa positive-fit connection.

The concept of FIG. 30 may be applied to arrangements with only onesonotrode (compare FIG. 25a ), for example by providing only the oneside of the first object that faces the sonotrode with a protrusion, orby providing both sides with a protrusion, with the side facing awayfrom the sonotrode having energy directing structures or being otherwisedesigned to be more inclined to absorb mechanical vibration energy thanthe side that faces the sonotrode.

The embodiment of FIG. 30 is an example of the concept of the portion(especially protrusion) of the first object that is in direct contactwith the sonotrode while the sonotrode acts on the second object 2 (or athird object) so that a sub-portion of the flow portion is formed at theinterface between the sonotrode 6 and the first object 1 to fill spaces.

This concept may also be used in configurations that are not accordingto the principle of providing a second and a third object, both withedges embedded in the first object material during the process. Rather,it may also be applied to embodiments in which merely the first objectis secured to the second object (and the first object optionally may beconfigured to serve as anchor for any further object). This isschematically sketched in FIG. 31. In this configuration, the sonotrodeacts from the side of the second object 2 (the lower side in FIG. 31)and presses the assembly of the second object 2 and the first object 1against a non-vibrating support (not shown in FIG. 31).

In embodiments like the ones of FIGS. 30 and 31 in which end portions ofthe first object are caused to become flowable, the end portions mayoptionally have shapes that favor such liquefaction. FIG. 31aschematically shows an according example in which a tubular portion 17with a reduced (lower in the orientation of FIG. 31a ) edge forms theend portion. This shape will cause an energy directing effect, andliquefaction at the contact between the tubular portion and thesonotrode (or, in another configuration, if the sonotrode acts from theside that in FIG. 31a is shown to be the upper side, between the tubularportion and a non-vibrating support or a portion of the second object orother non-vibrating object) will set in more swiftly than for shapes asillustrated in FIGS. 30 and 31.

FIG. 32 depicts an embodiment of the sub-group that includes bringingsecond and third objects 2, 4 into contact with the first object 1 froma same side. In FIG. 32, both, the second object 2 and the third object4 have a perforation 20, 40, around which the sheet material is deformedto project towards the first object 1. For securing the second and thirdobjects together by the first object, the second and third objects arepositioned one on the other, wherein the perforations are arrangedapproximately concentrically.

In the configuration of FIG. 32, similarly to FIG. 3a the vibration mayact on the first object from the side facing away from the first andsecond objects to embed the edges 21, 41 in the thermoplastic material,while the third object is placed against a non-vibrating support. Itwould be possible also to cause the mechanical vibration to impinge fromthe third object side or from both sides.

In the variant of FIG. 33, the second and third objects to be secured toeach other by the first object are not placed on top of each other butbesides each other. In this embodiment, the second object does not havea perforation. Rather, a peripheral edge 21 of the sheet portion is usedfor the process. A third object peripheral edge 41 is arranged adjacentthe second object peripheral edge 21, and the edges are, by the process(similarly to FIG. 3a /3 b) embedded in the thermoplastic material tosecure the first, second and third objects to each other.

In arrangements in which the edge is not an edge along a perforation butis especially a peripheral edge, it may advantageous if the peripheralpart along which the edge runs is provided with a bent structure orstructure having a corner so that the edge does not extend straight.This is especially the case if in-plane forces (shear forces) may beexpected to act on the connection between the objects. FIG. 34a veryschematically depicts peripheral parts of a second object 2 and a thirdobject 4 adjacent to each other, wherein the peripheral parts areprovided with a bend, here as part of a wave-like shape. Due to this,in-plane forces in both in-plane directions x and y can be absorbed bythe connection.

As illustrated in FIG. 34b , such a not straight structure of theperipheral part may not only be advantageous if the third object 4 isarranged beside the second object (solid line), like in FIG. 33. Rather,the dashed lines show further possible arrangements of the third objectthat is to be secured to the second object by the process.

Referring to FIGS. 3a , 33 and others the principle of couplingmechanical vibration energy into the first object for transferring thevibration energy to the interface with the second (and if applicablethird) object was described. In this, the parameters will generally bechosen so that the thermoplastic material does not substantially liquefyin contact with the sonotrode. FIGS. 30 and 31 describe embodiments inwhich in contrast to this targeted liquefaction at thesonotrode-first-object-interface is used to liquefy further portions ofthe thermoplastic material in order to fill structures.

FIGS. 35a and 35b schematically show another example where this is thecase. In FIG. 34a , the sonotrode is depicted to have a peripheralprotrusion 64 with a sloping shoulder that is equipped for makingflowable and deforming an edge portion of the first object and forlaterally confining the flow of the flowable material. This will lead toa well-defined smooth edge region of the assembly including the firstand second (and, if applicable, third) objects.

In FIGS. 35a and 35b a further optional feature is shown that isrealizable independent of the ‘liquefaction at thesonotrode-first-object-interface’ and/or confinement features. Thecombination of this optional feature with the well-defined shape causedby the protrusion or other dedicated sonotrode shape may, however, haveparticular advantages in special embodiments. This further optionalfeature is that the second object 2 has a deformed edge projectingtowards the first object, which edge goes along its full periphery ofthe second object and is entirely embedded in the first object material(FIG. 35b ). Therefore, the interface between the (proximally facing,upper in FIGS. 35a and 35b ) surface of the second object and thesurface of the first object (the distally facing surface in theconfiguration of FIGS. 35a and 35b ) is fully sealed. If an element (notshown) is for example attached to the second object at the surface thatfaces the first object, the approach results in a package thatcompletely seals off the element and protects it from moisture and otherpossible environmental influences.

This feature of causing a full periphery of the second object to becomeembedded in thermoplastic material of the first object can be done incombination with securing a third object 4 (as shown in FIGS. 35a and35b ) or without such combination, i.e. in a set-up without a thirdobject having a sheet-like portion with an edge to be embedded in thethermoplastic material.

FIG. 36 shows a further embodiment of a first object 1 (or a pluralityof first objects) to be mechanically secured to a second object. Thisfurther embodiment is an example of an embodiment in which thethermoplastic material is not only made flowable in contact with theedge but also at a contact face with a further portion of the secondobject. More in particular, in the shown embodiment the second objecthas a first portion 24 that is for example constituted by an essentiallyflat metal first sheet and a second portion 25 that includes the edgeand here may be formed by a second metal sheet attached to the firstmetal sheet and forming at least one hump with a perforation at the topof the hump. The first object has a head portion 102 and a shaft portion103, and for the process the shaft portion is introduced through theperforation until a distal end of the shaft portion 103 abuts againstthe second object's first portion 24 and/or a distally facing shoulderformed by the head portion 102 abuts against the edge of the secondobject's second portion. When the mechanical vibration energy impinges,both, the edge becomes embedded in the thermoplastic material and adistal end of the shaft portion becomes deformable and is pressedoutwards for the shaft portion to laterally expand so that the firstobject is additionally anchored by a kind of blind rivet effect. To thisend, the dimensions of the shaft portion may optionally be such that asubstantial portion of the volume defined underneath the hump (betweenthe first and second portions of the second object) is filled by thethermoplastic material.

A second object's first portion 24 in embodiments like the one of FIG.36 by the described approach may work as an anvil of the above-describedkind. Optionally, it may be deformed as described hereinbefore for theanvil to yield a flow guiding structure. According to an even furtheralternative, it may be replaced by a separate item having an anvilfunction.

In FIG. 36, the first object 1 shown on the right is depicted after theprocess, with the flow portion 14 including parts towards the distal endand at the interface with the edge.

FIG. 37 illustrates the option of a first object for an embodiment likethe one of FIG. 36 being collapsible, with a neck portion 105 forming adefault collapse location.

In variants of the embodiments of FIGS. 30, 31, 36, 37, the distal andof the first object may be shaped similarly to what is illustrated inFIG. 31a to cooperate with the portion (second object part, sonotrode,anvil) to work in a flow directing manner.

FIG. 38 depicts a process diagram for embodiments of the methoddescribed in this text. Curve 121 shows the pressing force appliedbetween the first and second objects, and curve 122 the vibration energypower, both as a function of the time. As shown in FIG. 38, in anoptional first phase 125 (pre-pressing), which first phase can be shortor can even be omitted, the first object is pressed against the secondobject without any vibration acting. This first phase may for example beadvantageous so as to make sure that when the vibration sets in, thepressing force and thereby a coupling force between the sonotrode andthe first object (or, if applicable, the second or other object of theassembly) is so that there is efficient coupling between the sonotrodeand the object, for example thereby preventing melting at the interfacebetween the sonotrode and the first object. In a second phase 126, thevibration is coupled into the assembly while the pressing force ismaintained. Depending on the configuration, the pressing force insteadof being constant as illustrated may follow a dedicated profile. In athird phase 127 (post-pressing phase), the vibration is switched off,but the pressing force is maintained for some more time until the flowportion has re-solidified to a sufficient extent to prevent anyundesired loosening or spring-back effects etc. During this third phase127, the second object along the edge may be even further pressed intothe first object. To this end, optionally (dashed line), the pressingforce may even be enhanced during the third phase.

FIG. 39 shows a configuration similar to previously describedconfigurations (for example the configuration of FIG. 3a ), but with anadditional element: An elastomeric sealing element 131 is placedrelative to the first and second objects prior to the step of applyingthe pressing force and the mechanical vibration. The sealing element isplaced at a location where the pressing force and the thereby causedrelative movement of the first and second object after onset of theliquefaction (making flowable) compresses the sealing element 131, herebetween the first and second objects. Thereby, an additional sealingeffect may be achieved. In the depicted configuration, the sealingelement 131 is a sealing ring surrounding the perforation 20 in thesecond object, whereby the connection between the first and secondobjects is completely sealed towards the first object side (the upperside in FIG. 39).

Also in embodiments with a sealing element compressed between the firstand second objects, the processing diagram may be similar to the oneshown in FIG. 38, however, the third phase 127 (post-pressing phase) maybe particularly long because of the spring-back effect that would becaused by the sealing element if the flow portion has not sufficientlyhardened.

Another example of an embodiment in which a sealing element 131 isplaced relative to the first and second objects prior to the onset ofthe pressing force and the vibration is shown in FIG. 41. In thisembodiment, which otherwise is similar to the embodiment of FIG. 8, thesealing element 131 is compressed between a connector piece 3 and thefirst object 1, thus on the other side of the first object relative tothe second object. Also in FIG. 41, the sealing element is illustratedto form a sealing ring. There is the option of placing an additionalsealing element at the location shown in FIG. 39 also in the embodimentof FIG. 41.

In embodiments like the ones of FIG. 39 and of FIG. 41, instead of anelastic sealing element 131, also a corresponding dose of an adhesivemay be used, for example dispensed to form a closed ring as is the casefor the sealing elements 131 illustrated.

FIG. 42 illustrates the principle that a third object 8 to be secured tothe first and second objects 1, 2 (or to be secured to one of the firstand second objects by means of the other one of the first and secondobjects) may be connected to the first object by an additionalpositive-fit connection between the first and third objects. To thisend, the third object 8 includes a structure that includes undercutswith respect to at least one direction (the axial direction in FIG. 42)into which thermoplastic material of the first object may flow. In theembodiment of FIG. 42, the structure is provide on a protrusion 45 ofthe third object 8 which during the process is pressed into material ofthe first object while mechanical vibration energy is coupled into thesystem. The objects are placed relative to one another so that theportion of the second object around the perforation is between the firstand third objects and the protrusion 45 the process reaches through theperforation of the second object and thereby comes into contact with thefirst object.

The protrusion 45 of the embodiment of FIG. 42 is comparable to acorresponding structure of a connector piece described hereinbefore, forexample referring to FIG. 5a /5 b or referring to FIG. 6 or 7 or 8.

A further feature of the embodiment of FIG. 42, which is independent ofshape of the third object that includes the protrusion with thepositive-fit structure, is that the third object 8 in contrast to theembodiments of FIGS. 5-8 is placed on the same side of the first objectas the second object. The process of causing vibration energy to impingethat results in embedding the edge of the second object and parts of thethird object (here: of the protrusion) will thus cause a backflow ofthermoplastic material towards the side of the second and third objects,whereby the space between the protrusion 45 and the sheet portion willbe at least partially filled.

Also, in configurations like the one of FIG. 42, the process will resultin the second object 2 being clamped between the first and thirdobjects.

FIG. 43 depicts a variant of the embodiment of FIG. 42, in which apositive-fit connection between the first and third objects includescausing material of the third object 8 to penetrate into an undercutstructure 141 of the first object 1. To this end, the third object maycomprise, at least in a region of the protrusion 45, thermoplasticmaterial that becomes flowable by the impact of the vibration energy andthe pressing force. The thermoplastic material of the third object insuch embodiments may be of a same composition as the one of the firstobject, or it may be different.

Depending on the material pairing of the thermoplastic materials of thefirst and third objects, in such embodiments also weld may resultbetween these objects, with or without an undercut structure beingpresent in one of the objects.

In embodiments, the method includes providing the second object with aplurality of attachment locations, each attachment location including anedge of the sheet portion, and coupling, for each attachment location,mechanical vibration energy into the assembly until a flow portion ofthe thermoplastic material due to friction heat generated between theedge and the thermoplastic material becomes flowable and flows aroundthe edge to at least partially embed the edge in the thermoplasticmaterial. This may be done simultaneously for all attachment location orfor sub-groups of attachment locations, or may be done sequentially forthe attachment locations. Each attachment location may for exampleinclude a perforation 20 of the kind described hereinbefore, with theedge running along the perforation.

FIG. 44 very schematically illustrates a second object 2 with aplurality of attachment locations 200. Generally, such attachmentlocations may be place in a regular or irregular arrangement,distributed in a two-dimensional or one-dimensional (along a line)manner. Especially, a two-dimensional arrangement of attachmentlocations will bring about stability with respect to tilting forces inall directions even if the attachment locations themselves arerelatively small and/or if the height h (see FIG. 1b ) is comparablysmall, for example due to a limited thickness of the first object. Thus,such a two-dimensional arrangement may cause a mechanically stableconnection even with very thin first objects.

One feature of the connections described hereinbefore in this text isthat the connection between the first and second objects (in embodimentslike the one of FIG. 34a /34 b including the third object) may absorbrelative forces in all in-plane directions in that the edge(s)comprise(s) portions running into different in-plane directions andprojecting into opposing directions.

This fact—that the edge includes both, portions that project at leastpartially into opposing direction (i.e., the directions into which oneof these portions projects has a component along an axis of thedirection into which an other one of these projections projects, whichcomponent has an opposite sign), and having edges running into differentdirections, may be advantageous in many cases, because it may provide aform locking into all in-plane directions. In hereinbefore describedembodiments, such portions are formed around one single perforation.

FIGS. 45a and 45b (FIG. 45b showing a section along plane B-B in FIG.45a ) show an alternative, in which the tongues 28 that form thedeformed section lock the first object only in one in-plane directionper perforation 20. However, the tongues 28 belonging to differentperforations project into different directions, including directionshaving components in opposite directions. Together, they lock the firstobject in all in-plane directions.

FIG. 46 illustrates principles of tolerance compensation. Mechanicalconnections by the present invention are suitable for tolerancecompensation in many ways: The location of attachment at the firstobject does not need to be pre-defined and can vary, the only conditionbeing that the edge is embedded in thermoplastic material—thus at thelocation of the edge 21 as well as where the material is to be embeddedthere has to be thermoplastic material.

-   -   Thus, the lateral position, the x-y position in the depicted        coordinate system, of the edge 21 (or to be more general: of the        attachment location) may thus vary within the according lateral        dimensions of the first object 1 or of a thermoplastic        attachment zone 112 thereof. In FIG. 46, m_(x) denotes a        potential mismatch of the relative, lateral, x-position between        two possible arrangements.    -   Also the relative axial position (z-position) can vary. In order        to have sufficient strength against axial pulling forces, the        dimension of the embedded portion P_(z) in a z-projection has to        have a certain minimal value P_(z, min). In practice, minimal        z-projection values of the embedded portion between 0.2 mm and 1        mm may be sufficient (this does not exclude higher values of        course), depending on the application. As long as this minimal        dimension is reached, the degree of how far the edge is pressed        into the first object (t_(z)) does not need to be pre-defined.        Thus, the relative z-position of the first and second objects        with respect to each other can vary within limits only given by        geometrical constraints (for example if surfaces abut against        each other) and by the named minimal dimension. In FIG. 46,        m_(z) illustrates a possible mismatch of relative z-positions        between two possible arrangements.

The zone that is affected by material flow when the sheet portion ispressed into the first object in FIG. 46 is denoted by 116.

In view of the considerations about the depth in z-direction and apossible z-tolerance, the angle α (see FIG. 1 b; FIG. 46 shows the angleβ=90°−α) is a possibly useful parameter. Generally, the larger the angleβ the larger the required minimum depth t_(z, min), as sketched in FIG.47 for different mechanical stress values σ for the connection towithstand.

Due to the illustrated possibility of tolerating a z-mismatch, also anangle mismatch may possibly be compensated by connections according tothe invention. This is very schematically illustrated in FIG. 48, wherethere is an angle mismatch γ between the sheet plane of the secondobject 2 and a corresponding plane of the first object.

FIG. 48 also illustrates (independently of tolerance compensation) theprinciple that the axial direction into which the sonotrode 6 pressesthe first and second objects against each other does not have to beperpendicular to the sheet plane.

In a many embodiments, the first object to be secured to the secondobject will not consist of the thermoplastic material but will have inaddition to thermoplastic portions also other portions. Especially, afirst object 1 may have a functional zone 111 in addition to at leastone attachment zone 112, as sketched in FIG. 49. The lateral dimensionsand z-dimension of the attachment zone 112 or attachment zones 112 maybe designed in accordance with the required tolerances.

In embodiments, the first object includes at least one functional zone111 that is unsuitable for attachment to an attachment location of asecond object, and a plurality of attachment zones 112 including thethermoplastic material.

In a group of embodiments with a functional zone and an attachment zone,the first object includes two thermoplastic material parts, the firstthermoplastic material part including the thermoplastic material that isused for embedding the edge, and the second thermoplastic material partincluding a different thermoplastic material, which differentthermoplastic material has different properties.

FIG. 72 illustrates an according example. The first thermoplasticmaterial part 356 defines and/or holds the functional elements. In FIG.72, schematically an inner thread 358 is illustrated. The secondthermoplastic material part/parts 357 serves/serve for attaching thefirst object 1 to the second object 2.

The thermoplastic material parts have different material properties.

-   -   The modulus of elasticity E of the first part may be greater,        for example much greater, than the according modulus of the        second part.    -   The (elastic) extensibility of the second part(s) 357 may be        much higher than the extensibility of the first part 356.

By this, for example different thermal expansion behaviors between thefirst object and the second objects may be compensated for.

Especially, a first object including two kinds of thermoplastic materialaccording to the present embodiments may be manufactured bytwo-component injection molding.

In embodiments, the invention concerns use of a method as described andclaimed in this text for attaching a first and a second object to eachother, wherein the second object has a at least one attachment location,especially a plurality of attachment locations, constituted by a (forexample deformed) portion defining the edge and projecting towards thefirst object, wherein a first tolerance for the positioning of theattachment location on the second object is greater than a secondtolerance corresponding to a tolerance for the final positioning of thefirst object with respect to the second object.

In other words, the invention is especially suited for situations wherea comparably precise relative positioning of the objects with respect toeach other (this includes the requirement of a positioning of one of theobjects with respect to a third object to which the other object issecured) may be required but where there is no precise positioning ofthe attachment locations. By this, therefore, a substantial gain inefficiency may be achieved, as precise relative positioning ofattachment locations may be a challenge in complicated set-ups, whereasthe present invention does not require such precise positioning.Nevertheless, the position of the one part (for example first object)relative to a complicated set-up that includes the other part may bevery precisely defined, including the possibility of a manual positionadjustment prior to the application of the vibration energy.

For example, the invention may include producing a plurality ofassemblies, each assembly including a first object secured to a secondobject, wherein the second object includes at least one attachmentlocation, wherein a standard deviation of the position of the attachmentlocation between the different assemblies is greater than a standarddeviation of the position of the objects with respect to each other(and/or the position of one of the objects with respect to a thirdobject to which the other object is secured).

FIGS. 50a and 50b show one possible way to precisely guide the positionof the first object 1 relative to the second object prior to theapplication of the mechanical vibration energy. A guiding tool 162having at least one guiding protrusion 163 holds the first object 1 bythe guiding protrusion 163 engaging in a lateral guiding indentation 161of the first object, wherein the guiding protrusion has a morepronounced curvature than the guiding indentation 161, whereby theguiding tool may hold the first object and precisely define its lateralposition, x-y-position in the coordinate system used in thisdescription, whereas free vibration along the z-axis is still possiblewhen a sonotrode is used to impinge on the first object 1. FIG. 50billustrates that for example a first object may have three lateralguiding indentations into which guiding protrusions of the guiding toolmay engage in a finger-like manner.

A further possibility of guiding the position of the first object withrespect to the second object for the attachment is by the sonotrode, asfor example illustrated in FIGS. 11 and 12.

The different embodiments of the invention have a large number ofapplications in various sectors of mechanical engineering andconstruction. A first example is very schematically illustrated in FIG.51. The first object 1 is a holder (with a holding structure 151) for anarticle 152 to be positioned to a frame, to which frame the secondobject 2 belongs. The frame may have a complicated configuration, andthe attachment locations 200 may for example be difficult to bepositioned precisely.

In an embodiment relating to the automotive industry, the frame may forexample be a car body or a part thereof, and the article may be a devicewith a location visible for the user, such as a technical, functional oroptically decorative element in the interior of the car, or any otherobject. The mechanic responsible for assembly may place the holder 1,for example with the article 152 already integrated, in a precise mannerwith respect to visible markings and/or reference points, so that apleasant impression is generated.

Attachment to the different attachment locations 200 may be donesimultaneously or one after the other.

A special feature of the embodiment of FIG. 51 (that is an option alsofor embodiments in which the first object has a purpose different frombeing a frame) is that the first object has an attachment flange 156against which the sonotrode 6 may be placed for attachment, theattachment flange defining an attachment zone surrounding a functionalzone.

An attachment flange forms a peripheral, laterally protruding portion ofthe first object 1. It may consist of the thermoplastic material; atleast a distal face includes the thermoplastic material. It defines aproximally facing incoupling surface 158, which is parallel to thedistal surface of the first object where the latter is in contact withthe edge of the second object 2. Thereby, even if the first object dueto its function has a complex shape that may be different from a shapehaving a plane distal surface (FIG. 51 for illustration purposes shows aplane distal surface, but different surface shapes are possible), a lesscomplex shape at the attachment location(s) becomes possible.

An attachment flange may but does not need to run around a fullperiphery of the first object.

For attaching, if the dimensions permit so, a single sonotrode runningaround the periphery of the first object may be used. Alternatively,especially if the energy input of such single sonotrode solution wouldbe too high, a plurality of sonotrodes may be used to impinge on thefirst object at different attachment locations simultaneously.

According to an even further option, one sonotrode or a plurality ofsonotrodes may be used to impinge on the object at the differentattachment locations sequentially. If this is the case, the vibrationalcoupling between the respective attachment location against which thesonotrode is pressed and the rest of the first object may be an issue.Especially, it may be necessary for the process to work properly thatnot too much vibration energy is conducted away from the attachmentlocation and coupled into the rest of the first object. Mechanicalcoupling between the part that has the attachment location and the restof the object may also be an issue because the anchoring processincludes moving the first object towards distally relative to the secondobject (or vice versa) at the attachment location at which the energy iscoupled into the first object (or second object), whereas at the otherattachment locations such movement is not possible.

Depending on the construction the use of an attachment flange beingperipheral and constituting a relatively flexible structure may as suchmay be sufficient for dealing with these requirements. In an alternativegroup of embodiments, the first object includes an elastic joint 350between the attachment flange 156 and a first object body. This is forexample illustrated in FIGS. 69 and 70. In the embodiment of FIG. 69,the elastic joint includes a neck that vibrationally de-couples theattachment flange from the first object body. In FIG. 70, rathergenerally a spring element that constitutes the elastic joint isdepicted.

A further optional feature of embodiments, especially but not only withan attachment flange, is shown in FIG. 71. The first object may includeat least one, for example a plurality of, dedicated, possibly marked,proximally facing coupling surface portions 159 that are positioned tocorrespond to attachment locations defined by the second object 2 (forexample at positions corresponding to positions of second objectperforations along which the edge extends). Such coupling surfaceportions are parallel to the distal surface portion that comes intocontact with the edge of the second object.

FIG. 119 shows an embodiment in which the attachment structure is not anannular flange but includes a plurality of attachment tongues 650 thatextend from a main body 660 outwardly. In the embodiment of FIG. 119, anoptional elastic joint 350 is illustrated between the main body and theattachment tongues. Embodiments with a plurality of discrete tonguesinstead of a flange that surrounds the main body are especially, but notonly, suited for situations in which the second object is not flat buthas a more complex 3D-shape as also schematically illustrated in FIG.119.

A further, independent feature is also shown in FIG. 119. The sonotrode6 includes a marking stamp feature. By this, a marking 671 is generatedin the process, as sketched in FIG. 120 showing a top view on one of theattachment tongues after the process. Such marking 671 may beadvantageous in production stages after the securing process, forexample for an operator to see where the second object underneath has aperforation, for example so that he can drive an element (screw, pin,etc.) through the assembly if necessary.

FIG. 52 illustrates a further application, namely the first object 1 isa base for fixing an article 172 with a frictional and/or snap-inengagement. For the snap-in engagement, the article 172 includes alateral protrusion 173 for engaging in a snap-in indentation 171 of thefirst object.

An even further application is illustrated very schematically in FIG.53. The deformed section of the second object 2 in this has a sufficientdimension for the first object 1 to be attached while the non-embeddedportions of the deformed section have still a considerable extension sothat the first object does not abut against the sheet plane. Dependingon how the edge runs, and if the second object is sufficientlyelastically deformable, this leaves the possibility of tilting movementsof the first object with respect to the second object, so that the firstand second objects are vibration-decoupled with respect to each other.

FIG. 54, shows an embodiment in which the second object 2 does not havea metal sheet in the narrow sense of the word, an edge of which formsthe edge. Rather, the second object is a die-cast metal object, forexample manufactured without any deformation step. The edge is belongsto a ridge-like protrusion 29 that is shaped by the die-cast process.

-   -   By this, arbitrary edge shapes become feasible. This includes        the possibility to have a plurality of ridge-like protrusions 29        and hence edges adjacent to each other.    -   Also, while in many embodiments, like in FIG. 54, the second        object will have an extended flat, plate-like or sheet-like        portion, this is not a requirement. Rather, because the edge is        formed by die-casting, the object may have any basic shape and        nevertheless include the edge. For example in the embodiments of        FIG. 54, the sheet-like portion is formed by the relatively        small ridge-like protrusion 29 that ends in the edge.

Hereinafter, principles of embodiments of the invention that include theconcept of adjusting a z-position of an adjustment part relative to ananchoring part are described. Generally, the z-direction in thedescribed and illustrated embodiments is assumed to be the directionperpendicular to the plane defined by the second object 2 around theattachment location (sheet plane), and it may correspond to thedirection (axis) into which the vibrating tool is pressed for securingthe first object to the second object. The principles describedhereinafter are to be understood as general principles of adjusting az-position and are not meant to be restricted to the shown specificgeometries and configuration. In all of the figures illustrating thisconcept, the second object is illustrated to have an attachment locationof the kind illustrated and described in FIGS. 1a -2 b. However, theconcept also applies to embodiments with other kinds of attachmentlocations implementing the approach according to the invention.

FIG. 55 illustrates a first example of an embodiment of the method thatincludes adjusting a z-position of an adjustment part 201 relative to ananchoring part, which anchoring part is constituted by the first object1. The embodiment belongs to the group of embodiments in which theadjustment part 201 includes thermoplastic material and is capable ofbeing welded to the anchoring part.

As for the other embodiments described in this text, the adjustment partmay optionally include functional elements, such as a connectingportion, a flange, an integrated function carrier (such as anelectronic/decorative or otherwise functional device), etc.

For carrying out the method, for example in a first stage, the firstobject 1 is secured to the second object 2 using a sonotrode 6 in theway described hereinbefore. The step of pressing the first objecttowards distally while the energy is coupled into the assembly in thismay be carried out until the distal face 12 comes into contact with theflat portion of the second object, whereupon the mechanical resistanceagainst a further distal movement of the first object 1 risessubstantially. Thereby, the z-position of the first object relative tothe second object is well-defined.

In a second stage, the position of the adjustment part 201 relative tothe first object 1 is adjusted and fixed. To this end, a furthersonotrode 206 advances the adjustment part towards distally against amechanical resistance while vibration is coupled into the sonotrode andfrom the sonotrode into the assembly. Because of the mechanicalresistance, friction heat is generated at the interface between thefirst object 1 and the adjustment part 201 so that material of bothparts becomes flowable. As a consequence, firstly a further distalmovement of the adjustment part becomes possible, and secondly, afterre-solidification, a weld is generated between the first object 1 andthe adjustment part 201. The advance movement is carried out until adesired z-position is reached, especially to compensate for tolerancevariations. The designation Δz shows the variation of possible relativez-positions.

The sonotrode 6 and the further sonotrode 206 are illustrated to beseparate devices. In alternative configurations, this is not necessary.For example, if the sonotrode is not symmetrical about the axis, thissonotrode may after an adjustment of its orientation (for example 90°twist) also use for the step of advancing and fixing the adjustmentpart.

According to yet another alternative, the (first) sonotrode 6 and thefurther sonotrode 206 may act simultaneously or partially simultaneously(in the latter case for example the further sonotrode starts actingbefore the—first—sonotrode 6 has stopped). The relative position of thefirst sonotrode 6 and the further sonotrode 206 defines the adjustmentof the z position.

In the depicted embodiment, the required mechanical resistance against aforward (distal) movement of the adjustment part is achieved by thefollowing geometrical properties:

-   -   The first object 1 (anchoring part) has an outer surface that is        stepped or tapering towards proximally;    -   The adjustment part has a tube shaped distal portion put over        the tapering portion of the anchoring part.

The embodiment of FIG. 56 is based on similar principles as theembodiments of FIG. 55. In contrast to the latter, however, theadjustment of the z-position of the adjustment part 201 relative to theanchoring part (first object 1) is not made by pressing advancing thefurther sonotrode by an adjustable distance but, for example previouslyto positioning the further sonotrode 206, by a movement of theadjustment part 201 relative to the anchoring part prior to the energyinput that fixes the adjustment part. In the depicted embodiment, theanchoring part has an outer thread 212 cooperating with an inner threadof the adjustment part 201 so that the position can be adjusted byturning the adjustment part 201 relative to the anchoring part securedto the second object 2. Thereafter, an energy input by the furthersonotrode 206 may act to weld the adjustment part relative to theanchoring part (first object 1) to fix the adjustment part to theanchoring part.

Instead of having an outer thread, the first object 1 could also have aninner thread cooperating with an outer thread of the adjustment part.Also other means for provisionally locking the z-position for thesubsequent fixing step are possible, for example a bayonet-like couplingwith different fixation depths (discrete adjustment), etc.

FIGS. 57a and 57b show an embodiment of an anchoring part (first object1) and a corresponding adjustment part 201, respectively. The adjustmentpart 201 has a ring shaped section shaped to be placed relative to theanchoring part so that a it is guided by a central proximal portion ofthe anchoring part. The adjustment part 201 is thereby rotatablerelative to the anchoring part. In this, a ramp section 262 of theadjustment part lies on a ramp section 261 of the anchoring part,whereby a rotation of the adjustment part relative to the anchoring partcauses the relative z position to shift, similar to a threadedconnection. At least one of the ramp sections 261, 262 may be corrugated(as schematically sketched) so that when in the subsequent fixing stepthe sonotrode presses the parts against each other, the parts do notshift relative to each other.

FIG. 58a shows an anchoring part being a first object 1 and anadjustment part 201, wherein one of the parts (in FIG. 58a theadjustment part) has a pattern of protrusions 221 facing towards theother one of the parts. For the adjustment and fixation, the adjustmentpart 201 is pressed against the anchoring part by a sonotrode whileenergy impinges so that the adjustment part is welded to the anchoringpart. The protrusions in this serve both, as energy directors and ascollapsible distance holders. The degree of how far the adjustment partis advanced into the anchoring part serves to adjust the relative zposition. FIGS. 58b and 58c show different cross section profiles ofprotrusions 221. The protrusions are arranged so that they do not formclosed contours so that air trapped between the parts can escape.

FIG. 59 illustrates a cross section of a corresponding arrangement afterthe welding process. The degree to which the openings 228 between theanchoring part and the adjustment part 201 remain depends on theadjusted relative z position.

The adjustment part in FIG. 59 for illustration purposes is shown toinclude a fastening portion 231 for clipping a further object onto thearrangement. Instead, as in the other embodiments, the adjustment part201 could include other structures or functional elements.

Instead of initially being separate parts, the adjustment part and theanchoring part can be provided as an already pre-assembled unity withthe adjustment part welded to the anchoring part. Then, the assembly ofboth parts serves as the first object. For the process, a (single)sonotrode acting on the proximal end face is used to couple energy intothe assembly and pressing the assembly against the second object. Due tothe superior energy directing characteristics of the edge of the secondobject, initially the thermoplastic material at the interface to thisedge will become flowable, and the assembly will be pressed into theportion of the second object that protrudes towards the proximal side.Only when the distal face 12 reaches the plane part, the resistance willincrease and the zone formed by the protrusions 221 will startcollapsing until a desired relative z position is reached.

FIG. 60 shows a variant in which in addition to the protrusions, aperipheral portion 222 of the adjustment part 201 at least partiallyencompasses a portion of the anchoring part (here: first object 1). Bythis measure, the guidance of the adjustment part during the process isfacilitated, and along the periphery 223 of the encompassed portion ofthe anchoring part another connection, for example weld, may begenerated.

FIG. 61a depicts another variant in which both, the anchoring part 241and the adjustment part 242 belong to the first object 1 and areone-piece with each other. A series of cavities 243 defines a collapsezone between the anchoring part 241 and the adjustment part 242. For theprocess, the sonotrode 6 acting on the proximal end face of the firstobject couples energy into the first object 1 and presses it against thesecond object 2. Due to the superior energy directing characteristics ofthe edge of the second object 2, initially the thermoplastic material atthe interface to this edge will become flowable, and the assembly willbe pressed into the portion of the second object that protrudes towardsthe proximal side (FIG. 61a ). Only when the distal face 12 reaches theplane part, the resistance will increase and the zone formed by theprotrusions 221 will start collapsing until a desired relative zposition is reached. FIG. 61b shows the result with a largely collapsedcollapse zone. The degree to which the collapse zone is cause tocollapse defines the z position adjustment.

The embodiments described referring to FIGS. 55-61 are all based on thefixing of the adjustment part relative to the anchoring part being amaterial fixing, i.e. after the process the adjustment part and theanchoring part are fused together.

In an alternative group of embodiments, instead the above-describedconcept of providing a connector piece, which may but does not need tobe initially separate from the first object, is used for implementingthe concept of adjusting a z-position of an adjustment part relative toan anchoring part. If the connector piece is not initially separate, thecorresponding piece in this text is also denoted “body of a notliquefiable material. In this alternative group of embodiments, arelative position of a first object thermoplastic material body (whichmay constitute the whole first object) and the piece (connector piece,not liquefiable body) is adjustable during the process. In this, theconnector piece serves as the adjustment part, and the first objectrelative to which it is anchored as the anchoring part.

FIG. 62 shows a first embodiment of this concept. The connector piece 3,similarly to FIG. 7, is a nut with an inner thread 39 and outerretaining structures 31. For the step of adjusting and fixing, asonotrode 206 may be used to press the connector piece into the firstobject, for example after the step of securing the first object 1 to thesecond object 2, and to couple vibration energy into the connector piece3 at the same time for making portions of the thermoplastic materialflowable to allow the connector piece to move into the material of thefirst object. The forward movement and the energy input are stopped oncethe connector piece 3 has reached the desired z position. After theportions of the thermoplastic material are re-solidified, by theirinterpenetrating the retaining structures they fix the z position andanchor the connector piece in the material of the first object 1.

In the depicted embodiment, the first object 1 is provided with anundersized (compared to the outer dimensions of the connector piece)opening 270 into which the connector piece is advanced. Optionally, asshown in FIG. 62, the opening is not a through opening but terminated bya bottom portion 271 so that the first object as in previously describedembodiments provides a sealing that seals the proximal side of thesecond object from the distal side thereof.

Alternatively, the connector piece could 3 itself be such that theopening that carries the thread is not a through opening but a blindopening, similarly to the connector piece of FIG. 7.

In even further alternatives, a sealing between the proximal and distalsides is not necessary, as is the case in examples described furtherhereinafter.

FIG. 63 shows a variant in which the opening 270 is a through openingand in which also the connector piece 3 is a nut with a through opening.

As a further optional feature of the embodiment of FIG. 63, the further,second sonotrode 206 that acts to press the connector piece into thefirst object and to adjust the z position acts not from the proximalside but from the distal side, i.e. not from the same side as the firstsonotrode 6 that is used to secure the first object 1 to the secondobject 2.

Independent of whether the z position of the connector piece is adjustedfrom the proximal side or from the distal side, a screw or otherfastener subsequently secured to the connector piece may be placed fromthe proximal or from the distal side.

Of course, instead of inserted/fixed by the effect of mechanicalvibration, the connector piece 3 may be inserted also by being pressedor, if it has a self-locking (external) thread, by simply being screwedinto the first object. The concept of adjusting the z positionindependent of the securing process remains the same.

FIGS. 64a and 64b depict a configuration in which the connector piece 3has a tapered portion cooperating with a tapered opening 252 of thefirst object. The degree to which the tapered portion of the connectorpiece 3 is pressed into the opening 252 by the sonotrode 206 defines therelative z position. As in the previous embodiments, the connector piecemay include outer coupling structures/retaining structures thatcooperate with liquefied and re-solidified thermoplastic materialportions to yield a positive-fit fixation of the connector piecerelative to the first object 1.

The following additional optional features shown in FIGS. 64a and 64bare independent of this concept and independent of each other:

-   -   The connector piece has a head portion forming a base for a        clip-on connection for a further part;    -   The first sonotrode 6 has a distal protrusion 62 that is used        for shaping and for example also at least partially generating        the opening 252. To this end, the first object initially, prior        to being secured to the second object 2, only has an undersized        preliminary opening 251, so that material of the first object is        displaced by the first sonotrode 6 during the process of        securing to the second object 2.

The concept of FIGS. 64a and 64b may work both, with a through opening252 or with a tapering blind opening.

FIG. 65 shows an embodiment in which the connector piece is not just aninsert (as in previously described embodiments, especially FIGS. 4a, 5a, 6-8, 15, 62-64 b) but has a peripheral collar portion encompassing andguiding a proximally facing portion of the first object. The peripheralcollar portion may be provided with inwardly facing retaining structures31. Similarly, a central portion, here with an inner thread 39, may haveoutwardly facing such retaining structures for cooperating with firstobject material into an opening of which the central portion is pressed(see FIG. 65).

FIGS. 66-68 illustrate different coupling structures for inserts. Theinserts may be inserts 16 that are present in an adjustment part 201,for example of the kind described referring to FIGS. 55-61 so that theassembly of the anchoring part and the adjustment part may serve asanchor for connecting a further part to the second object.Alternatively, the inserts may be inserts that are bodies ofnot-liquefiable material in the sense described hereinbefore. As yetanother alternative, the inserts may be connector pieces for exampleserving as adjustment parts in the hereinbefore discussed sense.

In FIG. 66, the insert is a nut with an inner thread and for exampleouter retaining structures. In FIG. 67, the insert includes a threadedbar to which a nut or other piece can be screwed. An anchored part 191is embedded in the thermoplastic material of the first object 1 oradjustment part 201, respectively. FIG. 68 similarly shows an insertwith a fastening head for a clip on connection. Other structures wouldof course also be possible.

Instead of being fastened to the thermoplastic material by having aportion that is embedded in it, also other connections, includingreleasable connections, are possible. For example, the insert and thefirst object/adjustment part may be provided with a bayonet couplingstructure, whereby the insert can be inserted in a coupling recess andsecured by a twisting movement.

The concept of adjusting a z-position of an adjustment part relative toan anchoring part hereinbefore has primarily been described referring toembodiments in which securing the first and second objects to each otheris carried out prior to the step of adjusting the z position. Inembodiments in which this is the case, the steps of securing and ofadjusting may optionally be carried out at different locations, forexample at different stations of a manufacturing line.

According to a further group of embodiments, adjusting the z-positionmay be carried out prior to securing. For example, initially measurementdata concerning particulars of the second object (or an assembly thatincludes the second object) and/or particulars of any other part (firstobject, other object to be secured to the first object) may be obtained.Based on this, the desired z-adjustment may be calculated in advance.Then, the z-adjustment may be carried out, for example based on anyconcept described in this text. Only after the z-adjustment has beencarried out, in these embodiments the securing takes place.

This sub-concept may be used for separating the steps in a manufacturingprocess. Especially, if the second object is comparably large or belongsto a comparably large pre-assembly (for example a vehicle body), thismay be advantageous because then the z-adjustment step may be carriedout at a much smaller station and does not delay the main process. Thisprinciple is very schematically illustrated in FIG. 107, in which 450illustrates a z-adjustment station and 451 illustrates a securingstation.

FIG. 121 shows a flowchart of a possible process according toembodiments of the invention which process includes an adjustment of theposition of a connector (or similar) with respect to the second objectfor example for tolerance compensation.

After start (S), in a first step 701 a possible tolerance mismatch ismeasured. Thereafter, a correct position or a position correction iscalculated (Step 702). If the connector or other functional part belongsto the first object and is integral with it, thereafter the first objectand the second object are positioned with respect to each other in thecalculated corrected position x,y,z, (angle) (Step 703); for exampleminus a z-offset accounting for a relative movement of the first andsecond objects during the subsequent step. Then, the securing step 704for securing the first object to the second object is carried out asdescribed in this text.

If, however, the connector includes an anchoring part and an adjustmentpart (if it is not one-piece or includes a collapsible/expandable zonefor example), a further distinction is made. In a first group, the aposition of the adjustment part relative to the anchoring part isadjusted (step 706) and fixed (step 707) prior to the securing step 708in which the anchoring part is secured to the second object. Theadjusting/fixing steps, which may optionally be combined, may be carriedout at a same station as the subsequent securing step, or may be carriedout at a different station.

In a second group, firstly the securing step 7011 securing the anchoringpart to the second object is carried out, and then the adjustment andfixing steps (that again may be combined) are carried out.

In embodiments of both groups, the fixing step and possibly also theadjustment step may be combined with the securing step, as explainedhereinbefore.

In embodiments of the second group, in contrast to what is shown in theflowchart, the measurement and calculation steps 701, 702 may be carriedout after the securing step 711.

In embodiments with or without z-adjustment, the extension of theconnection in z-direction may be an issue. For example, the first objectmay be a connector or belong to a connector for fastening a furtherobject to the second object, and this further object needs to berelatively close to the second object (low height connection).

For example the embodiments of FIGS. 62, 63, 64 b, 65 address this issueby providing the first object with an extending portion that extendsinto the perforation 20 of the second object and through the sheet plane(if defined), and by for example providing this portion of the firstobject with a retaining structure (inner thread 39) or other attachmentstructure for securing a further object to the second object via thefirst object.

An even further embodiment is illustrated in FIG. 116. The first objecthas a structure similar to the structure shown in FIG. 62. In contrastto this embodiment, an anvil 600 is used. The anvil includesradially-inwardly of the edge (referring to a center of the perforation)a directing protrusion that directs material flow distally of the secondobject 2 edge towards radially outwardly into an annular receivingdepression 602. The anvil includes a recess for accommodating theextending portion 269 that extends into the perforation and includes theopening 270.

The sonotrode 6 shown in FIG. 116 includes a guiding protrusion 62cooperating with the opening 270 to guide the sonotrode and furtherimplements the principle described hereinafter for example referring toFIG. 87. Both these features are independent of other features of theembodiment of FIG. 116 but may assist an optimized securing process.

FIG. 117 shows yet another embodiment (the sonotrode is not shown inFIG. 117). Similarly to the embodiment of FIG. 116, an anvil is used todirect material flow, and the anvil has a recess (which couldalternatively to the shown embodiment be a through opening) foraccommodating the extending portion 269.

A possible principle of any embodiments that include an anvil is alsoillustrated in FIG. 117. A volume of the receiving indentation 602(below the dashed line in FIG. 117) may be chosen to be somewhat smallerthan a volume of the thermoplastic material portion available forflowing. In FIG. 117, this available material portion corresponds to thevolume of an annular protrusion 605 of the first object. If the volumeof the receiving structure of the anvil is smaller than the availablevolume of the thermoplastic material, by applying a pressing forcebetween the first object on the one hand and the second object and anvilon the other hand a beneficial shaping pressure may be achieved.

A further option is sketched in FIGS. 111 and 112. The second object inaddition to at least one perforation 20 (three perforations 20 in thedepicted embodiment), along which the edge 21 extends, also includes anextension opening 510.

In contrast to the locations of the perforation(s), the second objectdoes not project towards the side of the first object along theextension opening 510. Therefore, the first object's z-extension aroundthe extension opening may be chosen freely, depending on therequirements. Also shape and dimensions of the fastening opening may bechosen independently of any properties required for the securingprocess.

In the embodiment of FIGS. 111 and 112, the first object 1 is has anextending portion being a collar 512 extending into the opening throughthe mouth of the extension opening 510. The collar may be essentiallytube-shaped, as illustrated in the figure. The connector piece 3 extendsinto the extension opening. The connector piece 3 cooperates with ajoining element 530 to secure a further object 501 to the second object.To this end, the joining element 530 is illustrated to have a headportion 531 to clamp the further object 501 to the connector piece.Other structures for securing the further object 501 to the connectorpiece could be applied alternatively or in addition to the illustratedone.

The connector piece 3 includes a head portion 521 and a shaft portion522, wherein the shaft portion can be secured to the collar 512 indifferent z positions, as illustrated by the double arrow Δz. Themechanical connection between the collar 512—or more generally: thefirst object—on the one hand and the shaft portion 522—or moregenerally: the connector piece 3—on the other hand may be any suitableconnection, including a screwed connection, other kinds of positive-fitconnection and/or force fit connection a material connection (such as aweld or an adhesive connection or a soldered connection), etc.

FIG. 112 moreover illustrates that the dimension of the collar thatextends through the mouth of the extension opening 510 may be such thatsome adjustment of the in-plane position (x-y-position) of the firstobject relative to the second object is possible.

FIG. 113 shows a variant of the configuration of FIGS. 111 and 112 inwhich the following additional features are realized:

-   -   The second object 2 and/or the further object are not        essentially plane but have an arbitrary 3D-shape. Accordingly, a        sheet plane is defined only locally around the perforations 20        and around the extension opening. The shape of the first object        is accordingly adapted.    -   The extending portion of the first object that extends through        the mouth of the extension opening and away from the side of the        further object 501 is not a collar open towards this side, but        the collar 512 is closed-off towards by a bottom portion 513.    -   The first object 1 does not consist of the thermoplastic        material but includes a first portion (body) constituting a        functional zone 111 and second portions constituting attachment        zones 112. The functional zone may be of a different material        than the attachment zones, especially a non-thermoplastic        material. Thereby, the functional zone material may for example        have a superior dimensional stability. Especially, the        functional zone may be metallic or of a harder plastic material        than the thermoplastic material of the attachment zones, such as        a composite material.        -   Especially, the second portions 112 that constitute the            attachment zones may be held relative to the first portion            constituting the functional zone by a positive-fit,            optionally in addition to other connection, such as adhesive            connection. In FIG. 113, the first portion is depicted to            have undercut indentations that are filled by the            thermoplastic that constitutes the second portions 112.    -   In FIG. 113, the first object 1 is depicted to form a fastening        structure being an inner thread that cooperates with an outer        thread of the connector piece. Other fastening structures,        including a sequence of bayonet fitting like structures at        different depths, glue channels, etc. are possible.

These features are independent of each other, i.e. it would be possibleto realize them individually or in any combination.

Referring to FIGS. 73-79, the principle of providing the contact sidewith structures, for example a pattern of indentations and protrusions,for reducing the required energy and force inputs, is described.

FIG. 73 shows an arrangement of a first object 1, a second object 2, anda sonotrode 6 positioned proximally of the first object 1. The firstobject on the contact side (distal side in the shown arrangement) has apattern of protrusions 301 and, between the protrusions, indentations302. Thereby, the flow portion of the thermoplastic material that flowsrelative to the second object during the process has a space to flow to.This is in contrast to embodiments without the structure on the contactside, where excess material displaced by the second object has to besqueezed out either through the perforation or sideways or has to flowback towards the second object against the pressing direction, in whichcase the forces and energy to be applied need to be higher.

As shown in more detail in FIG. 74, the following possible designcriteria may apply:

-   -   The overall volume V₁ of the protrusions may be approximately        equal to the overall volume V₂ of the indentations, i.e. the        middle plane of the contact side surface may be at approximately        equal distances from the peaks and valleys of the protrusions        and indentations, respectively.    -   The depth h₁ of the indentations may be smaller than the height        h₂ of the protruding section. This design criterion especially        applies of the connection between the first and second object        has to be sealing.

These criterial are independent of each other.

FIGS. 75 and 76, schematically showing views of the first object fromthe contact side, show possible patterns of indentations/protrusions.The radial pattern of FIG. 75 includes indentations 302 and protrusions301 that run radially from a central portion 304, which central portionin the process is aligned with the perforation of the second object andhas a smaller diameter than the latter. FIG. 76 illustrates a chessboard like pattern.

FIGS. 77-79 show alternative cross sections of protrusions that form thepattern of protrusions and indentations. The cross section shape of FIG.77 is similar to the rectangular shape of FIGS. 73 and 74 but isslightly tapered. FIG. 78 illustrates a pointed shape that has energydirecting properties (in many embodiments, the energy directingproperties of the edge of the second object are sufficient butadditional energy directing properties of the first object may bebeneficial in some situations). FIG. 79 shows a combination thatincludes a rectangular-cross-section main body of the protrusion 301plus energy directing ridges 305.

In FIGS. 80 and 81, an embodiment of a second object having a mainperforation 20 and a plurality of peripheral perforations 310distributed along a periphery of the main perforation is depicted. FIG.80 shows a top view on a second object, and FIG. 81 shows a first object1 attached to the second object 2 after the process. The peripheralperforations are smaller than the main perforation and are arranged in asection of the second object that projects away towards proximally froma second object sheet plane, i.e. the peripheral perforations arearranged where the sheet material is sloped with respect to the sheetplane (see FIG. 81). Moreover, the sheet along one or more of theperipheral perforations is deformed to project away, especially towardsproximally, from the curved surface defined by the projecting section,as illustrated in FIG. 81, where a peripheral perforation deformedsection 313 is illustrated to be bent towards proximally with respect tothe dashed line illustrating the curved surface.

FIG. 82 illustrates an embodiment in which the deformed section of thesecond object along the periphery is asymmetrical in that the height hof the projecting section differs as a function of the position alongthe edge of the second object. In the shown sectional view, the relation0≤h₁<h₂<d_(z) holds.

An asymmetrical deformed section like the one in FIG. 82 may be desiredfor example if asymmetrical loads are to be expected to impinge on theconnection between the objects. An asymmetrical deformed section mayalso be present because of manufacturing conditions. For example, thefastening axis (proximodistal axis; vertical axis in FIG. 82) may bedifferent from a deformation axis, especially if the second object isnot just plane but has a more complicated, 3D shape on a large scale.FIG. 83 illustrates this very schematically by showing a punching tool320 that causes the perforation and the deformation leading to thedeformed section around the perforation.

If the deformed section does not run around the full periphery, i.e. ifthere are portions with h=0, a possible condition may be that thedeformed section extends by more than 180° around the periphery, asillustrated in FIG. 84. Depending on the application and theconfiguration, this need not be the case, however (c.f. for example FIG.15).

FIG. 85 illustrates the possibility of z position control by anappropriately shaped first object contact side. The first object has adistally facing foot portion 341 peripherally of the location where itcomes into contact with the edge of the second object. The foot portionis also placed more laterally than the projecting section of the secondobject, whereby, when the first and second objects are pressed againsteach other when the vibration impinges, a relative movement of the firstand second objects against each other can be caused until the footportion abuts against the sheet portion where the sheet plane isdefined. Thereby, the z-position of the first object relative to thesecond object is defined by the dimension of the foot portion thatserves as a spacer.

FIG. 86 shows a simplified process diagram. The pressing force F, shownas a function of the relative position a, required to move the first andsecond objects against each other rises strongly when the foot portionabuts against the second object (dashed line). This may be used fordefining a threshold force F_(t). As soon as the required force reachesthe threshold level, the process may be stopped.

FIG. 87 illustrates the principle of restricting the coupling facebetween the sonotrode 6 and the first object 1 to a region the in-plane(x-y-) extension of which is restricted to a region tailored to theshape of the second object and to the location of the edge. For example,the coupling face may be restricted to a lane following the course ofthe edge of the second object 2. In embodiments with a perforation alongwhich the edge is formed, the coupling face is ring shaped with acentral opening.

To this end, in FIG. 87 the sonotrode is formed to include a distal ringshaped protrusion 331, whereby a central hollow space 332 is formedduring the process.

As shown in FIG. 88, showing a schematical vertical protection, thecoupling face 333 (dashed lines) extends to both sides of the edge 21.

Such a construction with a sonotrode forming a hollow space may featurethe additional benefit of making possible that a functional element thatmay be centrally located with respect to the perforation 20 does notcome into direct contact with the sonotrode. FIG. 89 illustrates anexample of a first object including a connector piece 3 being a threadedbar, whereas FIG. 90 shows a first object with a bushing as connectorpiece 3.

FIG. 91 shows that the principle of restricting the coupling face doesnot need to be implemented by shaping the sonotrode correspondingly, butthat in addition or as an alternative the proximal face of the firstobject 1 may be shaped to define the coupling face. In FIG. 91, thefirst object forms an indentation 335 to be aligned with the perforation20 in the second object 2. In FIG. 91, the distal outcoupling face ofthe sonotrode 6 is shown to be essentially flat; other shapes would bepossible also, for example including a guiding protrusion engaging witha guiding indentation of the first object (not shown).

In a group of embodiments, also, but not only, embodiments in which thecoupling face is adapted to the location of the perforation and theedge, the method includes adjusting a position, especially an in-plane(x-y-) position of the first object and/or of the sonotrode relative tothe second object.

In a first sub-group of this group, the position of the sonotrode 6 withrespect to the second object 2 is defined, for example by the machineryincluding a mounting frame. This first sub-group is schematically shownin FIG. 92. The position of the first object 1, which may be arrangedbetween the sonotrode and the second object 2, may be adjustable. Theprecision, by which the position of the first object may need to beadjusted, strongly depends on the nature and function of the firstobject and on the requirements.

A second sub-group of embodiments includes defining the position of thefirst object 1 relative to the sonotrode 6. The position of thefirst-object-sonotrode assembly relative to the second object may beadjustable. Again, the precision by which the x-y-position needs to beadjusted, may strongly depend on the structure and requirements. FIG. 93schematically illustrates the principle of the second sub-group. Therelative in-plane (x-y-) positions of the sonotrode and the first objectare fixed by a guiding protrusion 62 of the sonotrode cooperating with acorresponding guiding indentation of the first object. However, othermeans for defining a relative in-plane position exist.

FIGS. 94 and 95 refer to the first sub-group and illustrate a possibleset-up for holding and positioning the first object for the process. Theprinciple shown is similar to the one illustrated in FIGS. 50a and 50b .A possible requirement is that the means that guide the first objectneed to be such as to vibrationally de-couple the first object from theframework (for example constituted by a holding frame or a casing) withrespect to which they are mounted. In FIGS. 50a and 50b , this isachieved by the shape of the guiding tool. FIGS. 94 and 95, as analternative thereto, illustrate guiding tools being springs 361 that aremounted on adjustment tools 362 at least some of which have anadjustable x-y-position. The set-up may for example include three orfour such adjustment tools 362 with springs distributed around theperiphery of the first object 1. In case four adjustment tools arepresent, the adjustment tools that are at opposite positions may becoupled with each other and be movable together.

FIGS. 96-100 refer to the second sub-group of embodiments and illustratestructures defining and fixing, for the process, the in-plane positionof the first object 1 relative to the sonotrode 6. According to FIG. 96,the sonotrode may be provided with suction channels 371 through which avacuum can be applied, whereby the first object may be caused totemporarily stick to the proximal face of the sonotrode. As shown inFIG. 97, a combination of at least one such suction channel 371 withfixations possible. The sonotrode 6 of FIG. 97 for example includesguiding tips 373 that penetrate into the first object 1 and thereby fixthe lateral position. The penetration into the first object may becaused by a vacuum applied to the suction channel and/or by a pressingforce, possibly vibration assisted. In the latter case, material of thefirst object may locally be made flowable for the penetration of theguiding tips by the energy input.

If instead of pointed guiding tips 373, the sonotrode (or the firstobject) includes an annular ridge, the pressing of the first object andthe sonotrode against each other also addresses the possible issue ofleakage when vibration is coupled into the sonotrode. Otherwise, thesuction velocity has to be sufficient to compensate for such leakage tomaintain the vacuum.

The guiding tips 373 or other penetrating guiding means need not beundercut. An in-plane guidance and possibly also a temporary fullfixation may be caused by the guiding means reaching into material ofthe first object, in the latter case for example in a Morse cone likesituation (the shape of the guiding means being appropriately chosen).

A vacuum that sucks the first object towards the sonotrode 6 may beswitched off after the guiding tips (or other penetrating guiding means)have penetrated the first object.

FIG. 98 shows a further possibility. A guiding element 381, here being aguiding rod is laterally guided both, relative to the sonotrode 6 andrelative to the first object 1. A first bearing 382 in the sonotrode isconstituted by an O-ring being a loose fit bearing, and a second bearing383 is a tight-fit bearing relative to the first object, wherein by thesecond bearing the guiding element is also held with respect to axialmovements. Because one of the bearings (the first bearing 382 in thedepicted embodiment) is only a loose fit bearing, the vibration energythat is transmitted via the guiding element is minimized.

In the variant of FIG. 99, both, the first bearing 382 and the secondbearing 387 are loose fit bearings. An axial support is given by aninward flange 385 of the sonotrode 6 and an outward flange 384 of theguiding element 381 that cooperate with the O-ring that constitutes thefirst bearing to prevent the guiding element 381 from breaking loosefrom the sonotrode 6. An optional spring 388 may ensure that the axialposition relative to the sonotrode remains defined. The guiding element381 of the embodiment of FIG. 99 is, like the one of FIG. 98,essentially cylindrical with the exception of the outward flange 384.The cylinder symmetry is not necessarily the symmetry of a rotationalcylinder; a deviation from rotational symmetry may cause a guidance alsowith respect to rotational relative movements.

FIG. 100 shows an embodiment in which the first object is guided by aperipheral flange 391 of the sonotrode instead of (or in addition to) aguiding protrusion. The dashed lines show optional additional conicalpenetrating guiding elements 392 that during the process may penetrateinto material of the first object.

FIG. 101 illustrates that when a sonotrode couples mechanical vibrationinto the first object, the contact force between the first object andthe object against which it is pressed by the sonotrode, namely thesecond object, varies periodically. During the lower half-wave(illustrated by the shaded areas), the contact may be very weak or evenbe loose, and this may cause an uncontrolled sideways shifting(“swimming”) of the first object during the process absent any guidingmeans. This could be addressed by pressing the sonotrode with a higherforce against the first object. However, this influences the vibrationcoupling properties, and therefore the pressing force may be a parameterthat is not arbitrarily choosable. If however, an additional pressingforce F_(p) acts on the first object, the problem is solved (arrow inFIG. 101) if this additional pressing force is sufficient to compensatefor the “lift-off” effect during the lower half-wave periods.

An according set-up is illustrated in FIG. 102, where a hold-down tool395 is illustrated in addition to the sonotrode. The hold-down tool inthe depicted embodiment has an optional peripheral guiding flange. Also,the sonotrode is depicted to have at least one also optional conicalpenetrating guiding element 392.

For the process, it is sufficient if the hold-down tool 395 acts on thefirst object during an initial stage. As soon as the edge of the secondobject has penetrated the first object to some depth, the hold-downforce is not required any more. Therefore, the hold-down tool does notnecessarily need a forward drive mechanism for maintaining the pressingforce when the first object is moved towards distally during theprocess.

The embodiment of FIG. 102 may belong to the second sub-group, or it maybelong to a further sub-group with first and second objects having apre-defined position relative to one another (the first object positionbeing fixed by the hold-down tool), and, with the sonotrode positionbeing adjustable.

FIG. 103 depicts a fastener 400 having an anchoring plate 401 (or“fastener head”) and a fastening element 402 bonded thereto. Thefastening element can have any property of a state-of-the art fastenersuch as a threaded bolt (as depicted) a bolt without a thread, a pin, anut, a hook, an eyelet, a base for a bayonet coupling, etc. The fastenermay in this be constituted essentially like a fastener sold under thetrade name “bighead” and intended to be glued to a surface of anotherobject.

A fastener of this kind in a process of the invention may serve as asecond object. Especially, the anchoring plate 401 may be viewed assheet portion and may be provided with a plurality of openings 403 alongwhich an edge extends. This edge and/or the peripheral edge of theanchoring plate may be used as the edge in the approach according toembodiments of the invention. To this end, the anchoring plate along therespective edge may be deformed to be bended, especially towards theside from which the first object is to be brought into contact with theanchoring plate for the process.

FIG. 104 very schematically depicts a first possibility in which thecircumstances allow the mechanical vibration to be applied from thefirst object 1 side. The anchoring plate 401 is bent towards the firstobject side (for example, but not necessarily corresponding to the lowerside in the orientation of FIG. 103), whereby a bonding in the region ofthe opening(s) 403 may be caused, essentially as described hereinbefore.

In many configurations with a fastener of the kind mentioned referringto FIG. 103 it will not be possible or not be advantageous to couple thevibration into the first object, for example because the first object isa larger object, its backside is poorly accessible and/or for otherreasons. Then, the vibration may be coupled into the second object. Tothis end, the sonotrode 6 used for coupling the vibration into theassembly may be appropriately shaped.

FIG. 105 very schematically illustrates a first possibility. Thesonotrode has a receiving opening 410 having a mouth in the distaloutcoupling face, in which the fastening element 402 is received whenthe distal outcoupling face is pressed against the anchoring plate.Thereby the tool (sonotrode) and the second object are adapted to eachother for the tool to be pressed directly against a proximally facingsurface of the anchoring plate.

The tool may be equipped with a guiding structure, such as inwardlyfacing guiding protrusions 411 for the second object to be guidedrelative to the tool. Such guiding structure may especially engage thefastening element, as is the case for the schematically shown guidingprotrusions 411 of the embodiment shown in FIG. 105.

In embodiments, the guiding structure may be configured as fasteningstructure cooperating with the fastening element to temporarily fastenthe second object (faster) 2 to the sonotrode 6. This possibility isschematically shown in FIG. 106. In the example of FIG. 106, the secondobject/fastener has a fastening structure 402 being a nut secured, forexample welded, to the anchoring plate 401, and this nut serves as thefastening structure. The tool 6 includes a threaded protrusion 421adapted to the inner thread of the nut 402, whereby for the process thefastener can be screwed onto the tool.

Similar configurations are possible for other fastening elements aswell, for example an indentation with an inner thread for cooperatingwith a threaded bar of the fastener.

In the hereinbefore described embodiments, the mechanical vibration wasassumed to be longitudinal vibration, i.e. vibration in theproximodistal direction. This is not a requirement. As known for examplefrom ultrasonic welding of metallic parts, the vibration may also betransverse vibration. In the context of the present invention,transverse vibration may especially be an option for embodiments inwhich the vibration is coupled into the metallic part, i.e. into thesecond object instead of into the first object. For example inembodiments like the ones described referring to FIG. 106, in whichthere is a temporary fastening of the second object to the sonotrode, itwould be readily possible to couple transverse vibration from thesonotrode into the second object.

FIG. 108 very schematically illustrates an alternative. The sonotrodecouples vibration into the second object from a generally lateraldirection (in-plane direction with respect to the sheet plane, ifdefined), whereas a separate pressing tool 470 applies the requiredpressing force. This set-up corresponds to the lateral-drive set-up inultrasonic metal welding.

FIG. 109 shows a sonotrode 6 equipped for transversal oscillation. Thesonotrode 6 has a receiving opening 410 that is configured to receivethe fastening structure 402. Especially, in FIG. 109 the receivingopening is illustrated to have an inner thread adapted to the thread ofthe fastening structure being a threaded bar. The sonotrode 6 has aring-shaped skirt 480 that during the process is pressed against aperipheral part of the anchoring plate and thereby couples the pressingforce and, together with the receiving opening, the mechanical vibrationinto the anchoring plate 401. For symmetry reasons, the sonotrode 6shown in FIG. 109 in addition to the distal ring-shaped skirt 480 thatis pressed against the anchoring plate has a proximal ring-shaped skirt481. Due to this, it would be possible to carry out the process for twoassemblies in parallel, the sonotrode being clamped between two firstobjects pressed against the respective second objects that areintroduced from opposite sides (then, of course, the length of therespective fastening structures should correspond to at most half of theextension of the sonotrode in the direction of the receiving opening.Two more coupling locations could be present on the opposite sides ofthe sonotrode that are parallel to the drawing plane in FIG. 109.

Another sonotrode 6, suitable for example for a ‘wedge-reed’-likeconfiguration, is illustrated in FIG. 110. The sonotrode includes areceiving opening 410 for receiving the fastening structure (for examplethreaded bar). Similarly to the embodiments of FIGS. 109 and 106, thereceiving opening may optionally be equipped for a coupling to thefastening structure. The sonotrode is equipped and mounted fortransversal vibration of the distal end portion, for example by avibration coupled into the sonotrode by a coupler acting from sidewaysand causing a bending oscillation of the sonotrode, as schematicallyindicated in FIG. 110.

The sonotrode in the depicted embodiment instead of a ring-shaped skirtincludes a plurality of wings for coupling the vibration into lateralportions of the anchoring plate. An adaptation to a sonotrode with anoutcoupling skirt like in FIG. 109 or with another coupling face wouldbe readily possible.

Whereas the option of transversal vibration has primarily been describedreferring to second objects being fasteners having an anchoring plate,the concept may readily be applied to other embodiments also, especiallyto embodiment in which the vibration is coupled into the second object,including the embodiments of FIGS. 25-26, 30-31 and others.

EXAMPLE 1

A disc of ABS having a thickness of 4 mm was and a diameter of 19.5 mmwas attached to a metal sheet deformed as shown in FIGS. 1a and 1 b. Themetal sheet was a 0.8 mm steel sheet. The large diameter D was variedbetween 6, 8, and 12 mm, and the height h was set to a value between 2mm and 3 mm, and the angle α was chosen to be 20°. Using a commerciallyavailable ultrasonic welding apparatus (20 kHz) operated with anamplitude of about 60 μm and a power required of 1000-1500 W that waspressed against the proximal end face of the disc by a force starting at100 N and peaking at about 400 N, the method as shown in FIGS. 3a and 3bwas carried out. A solid connection was achieved, and after cooling toroom temperature, the disc could not be torn away from the sheet withoutdeforming the sheet.

The same was repeated with systematically varied parameters, namely

-   -   A 1.2 mm aluminum sheet instead of a steel sheet.    -   An angle of 40°    -   A height of 1.8 mm    -   Polyamide 66 with 30% Vol Glass Fibers as the disk material    -   PVC, PBT PET and PC 2000 as the disk materials;    -   A punched perforation with a smooth shape as shown in FIGS. 2a        and 2 b.

1-161. (canceled)
 162. A method of mechanically securing a first objectto a second object, the method comprising the steps of: providing thefirst object comprising a thermoplastic material in a solid state;providing the second object with a generally flat sheet portion havingan edge; positioning the first object relative to the second object toprovide an assembly comprising the first and second object, in whichassembly the edge is in contact with the thermoplastic material; whilethe edge is in contact with the thermoplastic material, couplingmechanical vibration energy into the assembly until a flow portion ofthe thermoplastic material due to friction heat generated between theedge and the thermoplastic material becomes flowable and flows aroundthe edge to at least partially embed the edge in the thermoplasticmaterial; stopping the mechanical vibration and causing thethermoplastic material to re-solidify, whereby the re-solidifiedthermoplastic material at least partially embedding the edge anchors thefirst object in the second object, wherein the first object comprises acontact side that comprises the thermoplastic material, wherein in thestep of positioning, in the assembly the edge is in contact with thecontact side, and wherein the contact side is structured by comprisingprotrusions and/or indentations.
 163. The method according to claim 162,wherein the contact side comprises a pattern of ridges and grooves. 164.The method according to claim 163, wherein the ridges and grooves extendradially from a center, and wherein the step of positioning comprisesaligning the center with a perforation of the second object.
 165. Themethod according to claim 162, wherein a volume of the indentationsapproximately corresponds to a volume of the protrusions.
 166. Themethod according to claim 162, wherein the sheet portion of the secondobject has a protruding section projecting away from the sheet planetowards the contact side and comprising the edge, and wherein a depth ofthe indentations is smaller than a height of the protruding section.167. A device, suitable for being used in the method according to claim162, the device comprising: a contact side and an opposite side that isopposite the contact side with respect to a z direction, andthermoplastic material in a solid state at least at an attachmentlocation on the contact side, wherein the device is capable of beingsecured to a second object that has a generally flat sheet portionhaving an edge, by a method that comprises coupling mechanical vibrationenergy into at least one of the device and of the second object whilethe contact side and the second object are pressed against each other,until a flow portion of the thermoplastic material due to friction heatgenerated between the edge and the thermoplastic material becomesflowable and flows around the edge to at least partially embed the edgein the thermoplastic material; and wherein the contact side isstructured by comprising protrusions and/or indentations.
 168. Thedevice according to claim 167, wherein the device is a connector andcomprises further a fastening structure equipped for cooperating with afastening structure of a further object to secure the further object tothe connector and to thereby connect the further object to the secondobject
 169. The connector according to claim 167, wherein the contactside comprises a pattern or ridges and grooves.
 170. The connectoraccording to claim 169, wherein the ridges and grooves extend radiallyfrom a center.
 171. The connector according to claim 167, wherein avolume of the indentations approximately corresponds to a volume of theprotrusions.
 172. A set comprising: a sonotrode comprising a distaloutcoupling face; and a first object comprising a contact side, anopposite side that is opposite the contact side with respect to a zdirection, and thermoplastic material in a solid state at least at anattachment location on the contact side; wherein the sonotrode isadapted to the first object to couple mechanical vibration energy intothe first object via a common coupling interface where the outcouplingface of the sonotrode is in contact with the opposite side of the firstobject, while the contact side of the first object is in contact with anedge formed by a second object that has a generally flat sheet portionhaving the edge, until a flow portion of the thermoplastic material dueto friction heat generated between the edge and the thermoplasticmaterial becomes flowable and flows around the edge to at leastpartially embed the edge in the thermoplastic material; whereby afterre-solidification of the thermoplastic material the first object issecured to the second object; and wherein the contact side is structuredby comprising protrusions and/or indentations.